An ambulance driver who is being prosecuted for speeding while transporting an emergency transplant organ has admitted breaking the speed limit again.

Mick Ferguson, 56, of Birkenshaw, Bradford, said the pending prosecution had not deterred him from speeding when he answered a blue light call last weekend to transport a liver from Middlesbrough to Leeds.

He said: "Until a court decides I was doing something wrong, I feel morally obliged to continue doing what I can to preserve life."

Mr Ferguson, who has worked for the ambulance service for 36 years, could lose his job if the prosecution brought against him by Lincolnshire Police goes ahead. In January, speed cameras on the A1 in Lincolnshire and Cambridge-shire recorded Mr Ferguson at 104mph as he raced from St James's Hospital, Leeds, to Addenbrookes Hospital, Cambridge, to deliver an organ for transplant. West Yorkshire Ambulance Service received letters from police in two areas, Lincolnshire and Cambridge-shire, asking them to explain why the limit was broken.

Despite explaining that Mr Ferguson was on a life-saving mission, Lincolnshire Police decided to prosecute but Cambridgeshire Police did not.

Mr Ferguson said: "This has never happened in organ transportation before. Usually we write back to the police and there is no further action."

Britain's General Union, the GMB, has written to the Home Secretary David Blunkett and Health Minister Alan Milburn to appeal for help.

John Durkin, GMB branch secretary, said breaking speed limits in the NHS was customary practice. He said: "We need the Government to clarify the law on blue light calls as this effects everyone."

Campaigners at the GMB, which has its regional office in Brighouse, have also started a petition which attracted 1,000 signatures in its first hour.

Mr Ferguson said: "The support I have received from work colleagues, NHS staff, former transplant patients and even parts of the police, has made me feel a lot better."

He said he has received calls from around the world, including Spain and Australia, from people who are outraged.

But Lincolnshire Chief Constable Richard Childs said: "Sometimes the decision, while the right one technically, might not be the right one in the eyes of the wider community until the broader issues are in the public domain."

Mr Ferguson's case will be heard by magistrates in Grantham, Linclonshire, on Wednesday, June 11.