‘Proportionality puts the burden on an administrative authority to justify its actions and requires some consideration of alternatives. In this respect it is a more rigorous test than one based on reasonableness’.
Alongside Illegality, reasonableness/unreasonableness is a major ground for judicial review of the administrative action in UK courts. With the advent of HRA and cases involving EC dimension, a new head of judicial review seems has been recognised by the court. This paper will concentrate on the concepts of reasonableness/unreasonableness and proportionality and make a comparative study between these two principles.
The challenge on the grounds of unreasonableness urges the court to hold that notwithstanding that there may be no firm evidence of improper purpose or concerning relevant/irrelevant considerations, nevertheless the court should intervene on the basis that the decision as the exercise of power is in substance one which no reasonable body could have come to.  . According to Greene M.R’s phraseology in Wednesbury  case, the decision is; ‘something so absurd that no sensible could ever dream that it lay within the powers of the authority.’
There is limit how far judiciary can intervene. It is not for the courts to substitute their choice as to how the discretion ought to have been while exercising power for that of the administrative authority. They should not substitute judgement. As Sir Thomas Bingham M.R stated in Cambridge Health Authority  case, the courts are not arbiters of the merit in the cases. 
The UK courts used the Wednesbury as a major instrument to control discretionary decisions, which have passed the legality of hurdles of propriety, purpose etc. 
When it came to application of the principle, according to PP Craig  , the court however developed the substantive meaning of unreasonableness in two ways.
1) Cases not concerned with rights:
These cases loosened the Wednesbury test although they were not concerned with rights. Examples are discretionary cases like matter involving planning permission cases-the test was applied in a way that made it closer to asking whether the court believed that the exercise of discretion was reasonable. It is really difficult to regard the subject-matter under attack in these cases as determinations which were so unreasonable that no reasonable authority could have made them.
In Balchin  , Sedly J held that a decision would be Wednesbury unreasonable if it disclosed an error of reasoning, which robbed the decision of its logical integrity, if such an error could be shown, then it was not necessary for the applicant to demonstrate that the decision maker was ‘temporarily unhinged’.
In Coughlan  , the court held that rationality covered not only decisions that defied comprehension but also those made by ‘flawed logic’. The loosening of Lord Greene’s test was supported by Lord Cooke in the ITF  case. He regarded Lord Greene’s formulation as tautologous and exaggerated. According to his Lordship, it is not essential to have such an extreme formulation in order to ensure that the courts remain within their proper bounds.
2) Cases concerned with rights:
The courts have varied the intensity with which they apply the Wednesbury test in cases concerned with rights. With Human Rights Act 1998, the growing recognition of the importance of rights was accommodated by modification of substantive meaning of unreasonableness.
Lord Bridge, in Brind  said that in cases concerned with rights, the courts must inquire whether a reasonable Secretary of State could reasonably have made the primary decision being challenged. The court should begin its inquiry by ensuring that only a compelling public interest would justify the invasion of rights.
Again as Lord Diplock stated in GCHQ  , the courts should be aware of their limited roles. The court should only intervene to ensure that the agency remained within the four corners of its powers but would only exercise very limited control over the rationality of the decisions through Wednesbury unreasonableness. As Craig Observed, “The premise differs in cases concerned with rights. The courts continue to accept that they should not substitute judgement. It is also generally accepted that traditional notion of sovereignty mean that the courts cannot invalidate primary legislation on the ground that it infringes rights. The courts do not, however, operate on the assumption that decisions about rights made by political arm of the government, or another public body must necessarily be accorded with the same respect or judicial deference as, for example, allocative decisions of an economic nature. The level of unreasonableness which the applicant must prove is less extreme than the traditional Wednesbury formula, and the court requires more compelling justification before it is willing to accept that an invasion of right is warranted.” 
Proportionality is general concept of EC law, and therefore UK courts are obliged to apply it in cases with a Community law dimension. The concept originates from German Administrative law. Proportionality works on the assumption that administrative action ought not to go beyond what is necessary to achieve its desired result and is often understood to bring courts much closer to reviewing the merits of the decision. In other words, if the measures are considered to do more harm than good in reaching a given objective, they are liable to be set aside. 
At a general level proportionality involves some idea of balance between interests or objectives, and that it embodies some sense of appropriate relationship between means and ends. 
The leading authority is the House of Lord’s decision in Brind  . In this case the applicants sought judicial review on a number of grounds. One of the grounds was that the directives were disproportionate. Their Lordship rejected the argument based upon proportionality. Lord Bridge, agreed with Lord Roskill that proportionality might at sometime be incorporated within our law. Lord Roskill, however, did not think that this was an appropriate case for such development, believing that this would lead the court into substituting their view for that of Home Secretary. Lord Ackner reasoned that if proportionality were to add something to the existing law, then it must be by imposing a more intensive standard of review than traditional Wednesbury unreasonableness. Accordingly, in later cases the courts have declined to apply proportionality as an independent standard of review.
Despite such a denial, there are a number of occasions where the courts have applied proportionality expressly or impliedly. This is evident in Hook  , where Lord Denning struck down a decision in part because the penalty was excessive and out of proportion to the offence. Recently, in Nadarajah  , Laws L.J. held that a public body could resile from a prima facie legitimate expectation only where it had a legal duty to do so, or where it was otherwise a proportionate response having regard to a legitimate aim pursued by the public body in the public interest. A similar trend is apparent in cases where the affected interest is fundamental right. The same approach was evident in other cases involving rights. It should nonetheless be recognised that the European Court on Human Rights did not think that this heightened scrutiny was sufficient to meet the necessity and proportionality tests under the European Convention on Human Rights. 
Human Rights Act 1998 and proportionality:
Proportionality was formally recognised as a freestanding ground of review under Human Rights Act and the first case decided before the House of Lords was Daly  . In this case, Lord Steyn held that there was a material difference between a rationality and test cast in terms of heightened scrutiny and a proportionality test. According to him, the intensity of review would be greater under proportionality. Proportionality could require the reviewing court to assess the balance struck by the decision-maker, not merely whether it was within the range of reasonable decision. The proportionality test could oblige the court to pay attention to the relative weight accorded to relevant interests, in a manner not generally done under traditional approach to review. As per Lord Steyn, the proper intensity of review was, guaranteed by the twin requirements that the limitation of the right was necessary in a democratic society, in the sense of meeting a pressing social need, and really was proportionate to the legitimate aim being pursued. 
The intensity of review under unreasonableness and proportionality:
It is clear from the discussion above that the proportionality principle can result in the courts attaching a relatively high value to the considerations such as those relating to fundamental rights. As Thomas Bingham MR observed in Smith  , “the more substantial the interference the more the court will require by way of justification before it was satisfied that the decision was reasonable.’ So, where an administrative decision has implications for fundamental rights, the courts will subject the decision to ‘anxious scrutiny’.” 
When it comes to HRA and Community law issues, the proportionality test imposes a more substantively intrusive ground (than that of unreasonableness) of judicial review on the government action by requiring the court to undertake a structured, multi stage examination of the content of the decision under challenge. Proportionality test requires the court to look much more closely at the political merits of the decision than it does under unreasonableness doctrine. But we have to keep in mind that proportionality principle is not so rigid a test as it seems to be. At least the jurisprudence of ECJ and ECtHR (where the principle originally comes from) shows that the test can be applied widely. It has been explained that ‘Under proportionality different margins of appreciation apply in different circumstances. Varying levels of intensity of review will be appreciated in different categories of case law and this will in turn, correspond to the different formulation of the test.’  In essence it is not, therefore, simply a question of seeking a right balance but of adapting the test to suit the needs of the situation in hand. As P Craig observed,
“It is readily apparent that if ECJ wishes to adopt a less intensive standard of review in a particular area then this will carry across to proportionality as well as to other grounds of illegality. A decision will only be overturned if it is ‘manifestly inappropriate’ to the objective being pursued. When proportionality is given that meaning, then there will be little difference between it and Wednesbury unreasonableness.” 
If we adopt Lord Cooke’s formulation of unreasonableness, (which he advocated for in ITF  and Daly  ) then the traditional principle comes much closer to proportionality principle. According to his Lordship, a decision would be overturned if it was one which a reasonable authority could or should not have made. The boundaries between courts and administration could be secured by a test which was less exaggerated than the traditional Wednesbury formulation. According to Craig, “it is difficult to see that factors which would be taken into account in this regard would be very different from proportionality test. The courts would, in some manner, shape or form want to know how necessary the measure was, and how suitable it was, for attaining the desired end. These are first two parts of the proportionality calculus. It is also possible that under Lord Cooke’s formulation a court might well, expressly or impliedly, look to see whether the challenged measure imposed excessive burdens on the applicant, the third part of proportionality formula. Again if we look at the earlier discussion of Wednesbury principle in cases concerned with rights, the level of unreasonableness which the applicant must prove is less extreme than in the traditional formula and the court requires more compelling justification before it is willing to accept that an invasion of rights was warranted.”  So at the end it depend which of the meanings of unreasonableness and proportionality ascribed by the court in a particular case. If we stick to original formulations, proportionality, no doubt, poses a higher standard of scrutiny especially when the cases involving HRA and EC issues.