The Conservatives have called for a full investigation into allegations that NHS patients are being put at risk by a laboratory staffing crisis

Researchers claim the problem has left unqualified workers handling important blood and tissue samples, according to a study.

A survey by the Institute of Biomedical Science (IBMS) - the professional body governing lab workers - says more than half of NHS laboratories are using inappropriate staff in place of biomedical scientists as low wages and poor promotion prospects deter those with qualifications.

There are about 280 NHS labs, which play a crucial role in the diagnosis of conditions such as cancer and HIV.

But, according to the IBMS study of 180 labs, 90% admitted they were severely understaffed and 60% regularly using unqualified workers to help with day-to-day tasks.

Some institutes said work that should have been done only by scientists was being left to secretaries and administration staff.

'Patients at risk'

Although most of the work left to unqualified staff was confined to basic tasks such as loading apparatus or grouping blood samples, BBC health correspondent Richard Hannaford says the IBMS believes patients are still being put at risk.

IBMS spokesman Alan Potter warned that, because of the vital nature of the work carried out, the situation could result in fatalities.

"If you are dealing with a staff that is recognised as being underpaid, overworked, over stressed, with low morale - this is a recipe for errors being made," he said.

But Lord Hunt, health minister in the Lords, dismissed the findings of the survey.

He said: "I wholly reject the suggestion that untrained, unqualified staff are being used to diagnose illnesses. the report is very long on allegations but short on facts."

Conservative health spokesman Dr Liam Fox responded: "This is a very serious accusation, and has been made by people who actually have patients' interests at heart.

"We should have a full investigation. The government's response has been dreadful. It's time that, if there is a problem, they investigate and take responsibility."

Akuna Anyarko Marfo, a junior biomedical scientist, earns just �9,000 a year working in London, after studying for three years for a science degree and two years on-job training.

She said: "We have got a lot of responsibility because we are assisting in saving people's lives. It is just a shame nobody knows that we exist.

"We are not asking for triple pay or anything like that, but we would like it to be equal to our experience."

Dr Jane Johnson, a consultant clinical cytologist at Nottingham City Hospital, told the BBC: "All laboratories are running short-staffed. If we want qualified and competent staff, we have to pay the going-rate for the job."

The Department of Health has admitted there is a problem with staffing levels and says it has offered staff on the lowest pay grade a 26% rise.

However, critics say qualified staff face years of training before they can hope to earn more money than supermarket checkout workers.