Campaigners for greater access to such treatment say health budget cuts, combined with regional variations in availability, has led to IVF - or in-vitro fertilisation - treatment by postcode.

The Sixth National Survey of the Funding and Provision of Infertility Services 1998 showed that the number of IVF treatment cycles per 100,000 in the population paid for by the NHS had fallen from 12.7 in 1997 to 10.8 in 1998.

This occurred despite guidelines suggesting that health authorities should pay for 40 treatment cycles per 100,000 to counter infertility effectively.

The survey was conducted by the College of Health and is published on Tuesday.

One in seven couples seek help

The College questioned all 124 health authorities and health boards in the UK.

Using information from the 95 that replied, the College found huge variability in availability of treatment.

Health authorities in Scotland provided 21.5 cycles per 100,000 people, while the figure was just 0.3 in the South West.

Waiting times varied too. Some couples saw a gynaecologist within one or two weeks of referral, while others have to wait up to three years.

Half the authorities had a waiting time of more than a year.

Most of them called for national guidance on how much treatment they should fund and which patients should qualify to get it.

While authorities tended to have eligibility criteria for fertility treatment, one in four of them had not reviewed their policy since 1993.

'NHS failing as a national service'

Caroline Spelman, Conservative MP for Meriden, led a Parliamentary adjournment debate on infertility last year.

She said: "The National Health Service should be a national service. However, the report shows this is clearly not the case.

"The availability of NHS-funded infertility treatment varies enormously purely because of your postcode.

"Most patients are either forced to seek private treatment or contribute to some of the cost, placing couples under great financial and emotional strain."

Clare Brown, of the National Infertility Awareness Campaign, said: "Health Authority spending on infertility services continues to be patchy and chaotic and there are huge differences in patient waiting times."

She added that health authorities tended to see IVF as a low priority and some people claimed it had low success rates.

But many clinics had success rates of up to 25% - the same as for natural methods. "You cannot ask for more," she said.

Tim Hedgeley, president of Issue, the National Fertility Association, said: "We are delighted to see the survey but saddened to note that Northern Ireland is bottom of the list.

"There should be full access to assisted reproduction treatment throughout the NHS, in line with its charter."

Institute could iron out inequalities

The National Institute for Clinical Excellence, which launches in April, has been set up to take care of irregularities highlighted in the survey.

The government has already commissioned its own survey into the availability of fertility treatment so the institute can get an idea of the scale of the problem.

The survey is due to be undertaken in March and its findings will be passed on to the institute.

A spokeswoman for the Department of Health said: "The government is concerned about these variations in access to NHS fertility services, has said that they are unacceptable and has pledged to tackle them."