But the much-criticised policy, which has led to the slaughter of millions of animals, was effective when implemented, they said.

"A prompt 24-48 hour culling policy would have resulted in a significantly smaller epidemic and fewer animals culled," Dr Bryan Grenfell, a zoology expert at Cambridge University, said at a select committee meeting.

But he said the mass slaughter was more effective than vaccinating animals because the multi-strained foot-and-mouth virus was difficult to immunise against and livestock would only be protected three to seven days after the injection.

Government scientists recommended the contiguous cull in March when 25 percent of the cases to date had been confirmed.

Nearly four million animals have been killed on over 2,000 farms - figures which led environmentalists, animal rights campaigners and some farmers to criticise the government for killing animals without the disease.

Many critics called on officials to start vaccinating animals against the highly infectious livestock disease as foot-and-mouth, first uncovered in February, lingered for months after UK officials said the battle was finally being won.

But the government's chief scientific adviser, Professor David King, reiterated that the mass cull was the only option.

"I would do the same again," he said.

"I believe this disease has been brought to a stop."

Professor Roy Anderson, an epidemiologist at London's Imperial College, said the cull had saved animals' lives.