Childless couples will be guaranteed only one attempt at test-tube baby treatment on the NHS in a move that sparked fury yesterday.

The Government's health 'rationing' watchdog, the National Institute of Clinical Excellence (NICE), will publish long-awaited guidelines this week recommending that women under 39 who are diagnosed infertile should benefit from at least three cycles of IVF provided free.

But although the guidelines were meant to sweep away the 'postcode lottery' of NHS fertility treatment - with many health authorities refusing to fund in vitro treatment - the Government has decided it will phase them in slowly.

Health Secretary John Reid is initially expected to set a minimum standard guaranteeing couples only one shot at IVF treatment. NHS trusts will have to offer three free cycles eventually, but there may be no fixed deadline for compliance.

His caution comes despite a report commissioned by MPs from fertility experts, to be published tomorrow, arguing the IVF boom would be affordable for the NHS.

Only a quarter of women get pregnant per IVF cycle, meaning many couples will still have to pay for further attempts. Reid will also make clear that couples who do not already have children will have priority.

Campaigners say NHS treatment is now so restricted that even men left infertile by cancer treatment, who froze sperm before starting chemo-therapy, are being turned away. A spokeswoman for the charity Infertility Network UK said many couples would be deeply disappointed.

'The Government needs to spell out clearly that it is going to take years to put the recommendations into practice,' she said. 'For a lot of couples who are going now for fertility treatment, their biological clocks are ticking and in two years it will probably be too late for them.'

Kevin Barron, chair of the Commons all-party infertility group, said estimates suggesting that to meet the NICE guidelines in full would cost £400 million were 'nonsense'.

'There have been a lot of scare tactics,' he added. 'If it is just one cycle, I would be very disappointed.'

The group's report cites the example of Belgium, where a free IVF service was funded by reducing twin and triplet births - expensive because of the likelihood of babies needing special care.

Doctors also want the NICE guidelines implemented in full. Richard Kennedy, secretary of the British Fertility Society, said: 'One cycle of treatment - which is by and large the sort of level of provision now - provides an opportunity to get pregnant but does not provide a reasonable chance of a pregnancy.'

Social criteria, such as whether or not a couple have children from a previous relationship, did not make clinical sense, he added. 'If you have a woman with secondary infertility (who has conceived before but cannot now) who is very young, she has got an extremely high chance of IVF working.

'But if you are talking about a woman of 39 who has got no children, that is the one less likely to succeed, so which is more cost effective?'

So few couples are currently eligible for full NHS fertility treatment that three-quarters of procedures are carried out privately. With IVF costing up to £3,000 per cycle, some couples spend more than £20,000 in their attempts to start a family.

In Scotland three cycles of IVF are routinely provided with married, childless couples given priority. Similar rules are likely in England and Wales. But campaigners say that discriminates against the infertile partner in second marriages.

Sheena Young, of the charity Infertility Network UK, said: 'You may have someone marrying a woman who has a child from a previous relationship. They start trying to have a family of their own, only to discover there is a fertility problem with the man.

'That means he is denied the treatment he needs, simply because he has married the wrong person in effect.'

Around 46,000 couples a year seek fertility treatment. It is not clear how many more would if three IVF cycles were available, but Kennedy's clinic in the Midlands expects an increase of 10 per cent.

However, costs would rise by more than that, as some patients currently treated privately switched to the NHS.

Tory health spokesman Andrew Lansley said: 'One has to ask what is the purpose of NICE's guidelines if Ministers arbitrarily reduce the standard that the NHS should aim for.

'The distress and disadvantage for couples who cannot afford private IVF treatment does require a better response from the NHS than has been offered up till now.'