The foot-and-mouth outbreak could have been started deliberately by someone who stole a test-tube of the virus from a laboratory in Britain.

The Sunday Express says a container of foot-and-mouth virus went missing from a secret Government lab at Porton Down in Wiltshire two months before the crisis began.

The disappearance was discovered during a routine audit of the sensitive unit, which also houses smallpox, TB, anthrax and Ebola. The newspaper says there are rumours the missing test-tube could have been taken by an animal rights activist.

The paper quotes a 'senior military source close to Porton Down' as saying: "A phial appears to have gone missing from one of the labs following a routine audit last year.

"Ministry officials were informed immediately and an investigation was launched initially by Special Branch and then by MI5, who are interested in the activities of animal rights protesters."

It says questions will be tabled in parliament about the Porton Down link this week. A Department of Health spokesman wouldn't comment but the paper said an agriculture ministry spokesman said the matter was being investigated.

The paper also claims it has seen documents confirming some sheep carried the virus long before the outbreak was confirmed on February 20. According to a Welsh vet, it was in Wales as early as January, says the paper.

Timber merchants say they were approached by the Ministry of Agriculture, Fisheries and Food in early February to supply wood for pyres. Agriculture minister Nick Brown insisted this was part of a "regular contingency planning exercise".

He told the paper: "There are a number of urban legends doing the rounds that the ministry knew about this disease before. That is not true."