The EU yesterday gave permission "in principle" for the limited vaccination of 180,000 cattle in Devon and Cumbria, the areas worst affected by the foot-and-mouth epidemic.
Officials from the Ministry of Agriculture said they were drafting legislation to implement the use of the vaccine should the British government decide to go ahead with the proposal.
The idea of a generalised vaccination programme is not on the agenda and the proposed scheme is being seen as a means of saving some of the national herd, rather than acting as a firebreak to contain the disease.
The scheme would be strictly limited to cattle in Cumbria and Devon which have spent the winter under shelter and would be slaughtered if they were allowed to roam freely.
In the House of Commons, the Prime Minister, Mr Blair, admitted he had underestimated the scale of the crisis in the early days of the outbreak.
Initially, officials estimated that there were as many as 2,000 sheep movements in January before the disease was confirmed. However, Mr Blair told MPs that it was "clear now that was an understatement" and there had been about 1.35 million sheep exported or moved around the country in January. "If this disease was incubating then, clearly it has been far more widespread than hitherto thought," Mr Blair said.
Downing Street said in some cases farmers moved sheep around the country up to eight times. One of the reasons was that farmers were attempting to qualify for EU quota payments. The movement of sheep in this way, officials said, probably contributed to the rapid spread of the disease.
In Cumbria, where the army is co-ordinating the pre-emptive cull of up to 500,000 sheep, Gen Sir Michael Jackson, Commander-in-Chief of British Land Forces, visited the disused airfield which is being turned into a mass grave to contain the carcasses.
Sir Michael said the army would take part in the operation as long as the personnel were required. Earlier, Mr Blair urged the public to go back to the countryside to show tourists and the rest of the country that Britain was open for business. Speaking to the British Chambers of Commerce conference in London, Mr Blair said tourism bookings were down in areas not affected by foot-and-mouth because of a general perception that the countryside was closed.
As he warned that the cost to the tourism industry was already reaching £100 million sterling each week, he said tourist attractions and country paths were gradually reopening in areas away from farms and infected regions.