A union claims virtually every hospital in the country faces a shortfall in key lab workers - and this could place health at risk.

A survey of more than 300 hospital pathology departments carried out by the Manufacturing, Science and Finance (MSF) Union found that two out of three had long-term unfilled vacancies.

The union blames poor pay rates for an exodus of workers from the profession.

Laboratory scientific officers in the UK are responsible for checking blood samples for infectious diseases or poisons.

'Doomed to failure'

The union claims that the vacancies are placing patients in danger.

MSF general secretary Roger Lyons said: "There are serious dangers to the public and the NHS from this recruitment crisis.

"There are 2,500 empty white coats that should be filled by scientists undertaking lifesaving tests for NHS patients.

"Unless urgent action is taken, the government's plan to turn the NHS round is doomed to failure."

The union said the problem was particularly bad in London, where it is even harder to live on a starting salary of approximately �9,500.

At University College London, where there are 30 posts, there were 24 vacancies.

Other hospitals with vacancies, according to the survey, included the John Radcliffe Hospital in Oxford, the Royal Liverpool University Hospital, and the Queens Medical Centre in Nottingham.

The Department of Health said it had made above-inflation pay rises to scientific officers.

A spokesman said: "Our latest pay offer would mean that grade I officers would receive an increase of 7.1%, while trainees could receive pay rises of up to 26%."

He said a review of recruitment in NHS labs could make working arrangements more flexible and convenient.

The MSF has already highlighted a shortage of medical technical officers, who are responsible for operating and maintaining some specialised hospital equipment.