The medicine regulator faces a legal challenge this week over its ruling that thousands of women with thinning bones should be denied effective treatment on the NHS.

Draft guidance from the National Institute for Health and Clinical Excellence (NICE) states that doctors should prescribe the cheapest drug available to women with the early signs of osteoporosis, even though up to one in five patients cannot take it.

The National Osteoporosis Society and the drug manufacturer Servier say that this is unethical and will do nothing to prevent fragility fractures that contribute to 13,000 premature deaths a year, as well as causing widespread disability and pain.

They will contest the NICE guidance in the High Court, as part of a full judicial review, claiming that the watchdog has not been transparent about its processes and is infringing the human rights of patients by denying them alternative medication on the ground of disability.

NICE denies that it has acted illegally. But in a letter to The Times last September, 40 experts called on the watchdog to reconsider its decision, calling it “unethical and short-sighted”.

Half of women and one in five men over the age of 50 will develop osteoporosis, in which the spine, wrist and hips become thin and fracture easily.

While bone-strengthening drugs are available, the side-effects of alendronate, which costs £50 a year, include crippling stomach pains and indigestion, while the medication is difficult to take — requiring patients to stand or sit for 30 minutes while it is absorbed.

The guidelines mean that a woman in her early seventies who cannot tolerate alendronate would have to get up to 60 per cent worse — using a clinical scoring system — to qualify for strontium ranelate, an alternative medication that costs £17 a month.

Nick Rijke, a spokesman for the National Osteoporosis Society, said: “Already there are more than 70,000 hip fractures a year which result in 13,000 deaths and cost the public purse £2.3 billion.

“Yet with effective treatment, many of these fractures could be prevented, not only saving lives, but saving the taxpayer money at the same time.”

Andrew Dillon, the chief executive of NICE, said that the recommendations on osteoporosis had been “a complex set of guidance to produce”, but added that he was confident that NICE had acted lawfully and that the claim would be dismissed.

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