The National Institute for Clinical Excellence (Nice), which recommends which medical procedures should be available on the NHS, was never designed to be popular.

Since its establishment in 1999 to combat the “postcode lottery”, it has made plenty of hard choices about judicious use of taxpayers’ money. It has ruled against the prescription of beta interferon for multiple sclerosis, and restricted access to three bowel cancer drugs. But few decisions have proved as controversial as its recommendation against four medications for Alzheimer’s disease.

On the face of it, the proposal not to fund donepezil, rivastigmine, galantamine and memantine looks perverse. Trials have established that these can delay the progression of Alzheimer’s in some early-stage patients. No other therapy is available for one of the most devastating of illnesses. No wonder that charities, psychiatrists and politicians united to demand a rethink.

Yet Nice’s appraisal committee has reached the right conclusion under its terms of reference. It must evaluate not just effectiveness but cost-effectiveness, too, and even at a price of £2.50 per patient per day, these drugs do not pass muster.

Nice assesses therapies according to their impact on quality-adjusted life years — a measure of both extended life and improved health. Treatments for diseases of old age such as Alzheimer’s, which merely delay rather than arrest their development, do not score well on this index. Public healthcare funding is a game of priorities: money for one therapy means none for something else. Nice has been playing strictly by rules that do not suit conditions that afflict the elderly.

There is a strong argument that the rigid criteria are not appropriate in this particular case. Alzheimer’s places a major burden on family members: delayed symptoms can keep spouses or children at work but Nice does not take this into account. The idea of progressively losing our minds, with little prospect of a cure, is very frightening, and removing the only frontline treatment doesn’t inspire hope.

These factors, along with the protests, explain why Nice this week refused to affirm the appraisal committee’s advice not to fund the drugs. It has instead delayed a final decision pending further information from the manufacturers. This, though, is a misguided fudge that will satisfy no one and merely postpones a difficult choice that has to be taken.

Nice’s chief executive, Andrew Dillon, is clutching at straws by asking the drug companies for unpublished data about effects for particular patient groups. It is a sure bet that none will be forthcoming. Firms have been caught before sitting on results that do not suit their marketing strategies but are unlikely to have suppressed work that supports their interests. Clive Ballard of the Alzheimer’s Society was right to call the delay a “cop-out ”.

The institute ought not to be twisting its usual standards for populist reasons. It is there to provide hard- nosed advice and the appraisal committee’s verdict — which it has reiterated — should have been endorsed.

That would have placed the final decision about the availability of the drugs squarely where it belongs — with Patricia Hewitt, the Health Secretary. Ministers have overruled Nice before — on beta interferon and on offering one cycle of free IVF instead of the recommended three — but the choice to step beyond dispassionate cost-benefit analysis and introduce other factors to the mix is a political one.

Instead of leaning on Nice to reach a palatable verdict — and voices from junior ministers to Tony Blair urged it to reconsider its advice — the Government should leave the bean-counters alone to do their job. If their final decision is unacceptable, ministers must explain why it should not be implemented. Interference with the assessment process undermines the whole point of Nice for the sake of ducking a tough call.

Mark Henderson is the Times science correspondent

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