The osteoporosis drug you only have to take once a year - that may never reach the NHS

But despite its high success rate, campaigners warn it may never be prescribed on the NHS on the grounds of cost.

It comes as osteoporosis specialists challenge proposed prescription restrictions put forward by the National Institute for Health and Clinical Excellence, the Health Service's rationing body.

Trials on the new treatment Aclasta show it cuts the risk of hip fractures in post-menopausal women by 41 per cent and reduces spinal fractures by 70 per cent if taken for three years.

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Some 60,000 hip fractures and 120,000 fractures of the spine occur annually in the UK. Each broken hip costs £12,000 on average to treat.

But under new NICE proposals, doctors will be allowed only to use the cheapest drug available. For osteoporosis sufferers this would mean being treated with Alendronate, which costs 14p a day.

A quarter of women taking it go on to develop chronic side effects, including stomach pains, or do not respond to treatment.

One of the biggest advantages of Aclasta is that it needs only to be taken once a year, compared to other monthly alternatives.

It has proved to be especially useful for patients who have difficulty swallowing or digesting tablets. Many are required to fast before taking the current drugs and have to stay upright for an hour afterwards.

Made by pharmaceutical company Novartis, Aclasta is given as a drip into the arm, which takes 15 minutes. It is normally administered in hospital outpatient clinics although, under NHS reforms, it may soon be allowed in GP surgeries.

Aclasta costs £284 a year - about £5.50 a day - which is similar to the cost of current monthly treatments used by the Health Service, but under threat from the new NICE guidelines.

David Reid, Professor of Rheumatology at the University of Aberdeen, said: "Preventing hip fractures remains one of the main aims of treating osteoporosis. Three months after a hip fracture, nearly one in five elderly patients will die.

"Reducing hip fractures by 41 per cent is therefore highly clinically significant."

The drug will now be evaluated by NICE and its equivalent body in Scotland to determine whether it offers value for money, although no timetable has yet been set.

However, campaigners are warning that the proposals for prescription restrictions in England will effectively block the drug.

The National Osteoporosis Society is appealing against them, saying hundreds of thousands of patients will be left untreated.

Nick Rijke, director of public and external affairs at the NOS, said: "The addition of another option for GPs to use in treating osteoporosis should be great news.

"But NICE has a stranglehold on medical progress, taking far too long to consider the effectiveness of drugs and then becoming so obsessed with cost that many people cannot benefit from the advances being made in medical science.

"If NICE guidance goes ahead unchanged, patients will be at the whim of purse-holding PCTs. This brings back postcode prescribing."