Margaret Beckett fails to address public concern with her attempt to explain the thinking behind the bizarre way this problem was made public

Peter Ainsworth Shadow rural affairs secretary

Rural affairs minister Margaret Beckett has been attacked over the way the mix-up was revealed as the first confused press release was issued late in the evening.

The government is still recovering from the row over spin doctor Jo Moore's e-mailed suggestion to "bury" news in the aftermath of the World Trade Center attacks.

An investigation is under way to discover how the sheep and brain tissue samples became mixed up at an Institute of Animal Health laboratory in Edinburgh.

Mrs Beckett has already insisted she wanted the information to be made public as soon as possible.

Possible contamination

But an official from her department told the Observer: "We had known for a while that the experiment had been undermined by contamination issues."

"But we thought that just part of the experiment had been affected, rather than the whole thing."

A spokesman for Defra said only the question of possible contamination was raised with the department three months ago.

He said the material had originally been collected for other purposes by scientists and had not met with the same standard of stringent checks.

When the material was used for the BSE research, the spokesman said, scientists posed the question that it would not have met with the same checks, which raised the issue of cross-contamination.

IAH scientists mixed up their samples

"Someone brought to our attention a potential problem," he added.

The Conservatives have urged Ms Beckett to make an emergency statement to the Commons about the possible risks of BSE in sheep, described as "theoretical" by the minister.

The Tories said the way the release of the news had been handled "beggared belief", while the Liberal Democrats said Ms Beckett had "a lot of awkward questions to answer".

Shadow rural affairs secretary Peter Ainsworth said: "Margaret Beckett fails to address public concern with her attempt to explain the thinking behind the bizarre way this problem was made public.

"She fails to explain how this situation arose in the first place and does nothing to comfort us as to the safety of sheep meat.

'Further bungling'

"I call on Mrs Beckett to make a full statement to the House of Commons about her handling of this situation and the safety of British lamb.

"British farmers need no further bungling by this government."

Ms Beckett told the BBC: "I gave instructions, perhaps in error, that the statement that had been drafted to explain what we knew - and bear in mind the whole point about this is that there is confusion - that the limited amount that we knew should be put into the public domain as soon as possible.

"Yes, we didn't have time to brief specialist correspondents, we hadn't known for long enough, yes we didn't wait and have a press conference in the morning.

"I feel strongly confident that if we had we would have been accused of trying to bury the information altogether."

Ms Beckett said she first found out the experiment had gone wrong last Wednesday afternoon.

"The press release was short, simple, we put it out as fast as we could once as we had as a matter of courtesy notified and checked with the people [concerned]."