By Martin Hutchinson BBC News Online health staff in Madrid

Samples were not kept apart

Only a few have separate storage systems for sperm from HIV positive men - or make sure that treatments to remove the virus from sperm have worked before they use it in IVF treatments.

The demand for fertility treatments from HIV positive patients is growing fast, according to the survey carried out by experts from the Chelsea and Westminster Hospital in London.

We feel that separate storage facilities are essential Dr Leila Frodsham, Chelsea and Westminster Hospital

This is partly due to the success of antiretroviral drugs in extending the lives of patients, who might previously not even considered the possibility of having a baby.

However, the survey shows that only a handful of clinics are doing all they can to protect their patients from the risk of HIV transmission.

Small safety

It found that only 6% of the clinics who replied to the survey had separate storage facilities for sperm from HIV positive patients, which would minimise the risk of infected semen being inadvertently used in another couple's IVF treatment.

Dr Leila Frodsham, who presented the research at the annual European Society of Human Reproduction and Embryology meeting in Madrid on Tuesday, said: "This is a very small minority.

"While there has never been a case of HIV being transmitted in this way, we know that hepatitis C can be.

"We feel that separate storage facilities are essential.

Many clinics were "failing to meet minimum safety standards", she said.

Of the 12 clinics that offered a technique called "sperm washing", which aims to flush any remaining HIV from the surface of the sperm, only two carried out further testing afterwards to make sure there was no HIV present.

"We know that sperm washing fails in about 5% of cases, " she said: "This puts women and the unborn child at a significant risk of seroconversion (infection)."

Too expensive

A lack of government funding of sperm washing in clinics meant that HIV positive couples unable to afford the procedure privately would be more likely to have unprotected sex in their desire to have a child.

Dr Frodsham said: "Sperm washing is not a fertility treatment - it should be funded as an HIV prevention measure."

A spokesman for the HIV charity the Terrence Higgins Trust said that the procedures to prevent cross-infection were "straightforward", and that all clinics should be able to follow them.