Thousands of poultry workers are to be offered free influenza jabs in an attempt to stop new forms of bird flu emerging.

More than 60,000 farmers, vets and others who have close contact with poultry will be eligible for vaccinations against seasonal human flu.

The Department of Health hopes that the vaccine will cut the risk that the workers may catch human and bird flu viruses at the same time, allowing the viruses to mutate and create new, contagious strains.

Poultry workers will join the elderly, sufferers of chronic conditions and their carers as part of the “at-risk” groups considered most vulnerable to flu.

At a briefing to announce the plans, Fred Landeg, the Chief Veterinary Officer, said that very cold weather could increase the risk of bird flu coming to Britain this year.

David Salisbury, the Department of Health’s director of immunisation, emphasised yesterday that avian flu was a disease of birds and posed a risk only to people who had prolonged contact with infected birds. He said: “The immunisation programme we are announcing today is a precautionary measure which reduces any very low risk of a pandemic flu virus emerging in the UK. There are concerns that those who work in close contact with poultry and who could also contract human seasonal influenza could act as a mixing vessel for new forms of bird flu if they became infected with an existing strain.

“You end up with something that has genetic material from two different viruses and then you have no immunity at all because you have got a completely new virus. These are theoretical concerns but are viewed as significant and so should be managed.”

He said that a cold spell in Eastern Europe could cause lakes and the sea to freeze, prompting migratory birds to head west towards Britain in search of open water.

Information packs are being sent to all registered poultry farmers — those who keep flocks of more than 50 birds — as well as approved slaughterhouses in England.

People regarded as poultry workers include some members of the State Veterinary Service, and those who routinely access poultry-rearing or egg-production areas, those who catch, handle and kill live birds and those who regularly collect and remove poultry manure from enclosed units.

The Department of Health has bought additional doses of the seasonal flu jab for the programme, which will run from January 22 to the end of March.

It said that it would not take vaccination doses from stocks intended for other high-risk groups.

It has also pledged an extra £500,000 for NHS trusts to administer the vaccinations.

Earlier this year there were fears that vulnerable people could miss out on their jab after the Government confirmed stocks would arrive late.

But Dr Salisbury said that, by December, the supply had overtaken that for the same period the previous year.