Environment Secretary David Miliband has defended the government's handling of Hungarian poultry imports after the outbreak of bird flu in Suffolk.
David Miliband said vets had not advised a turkey ban
He said a ban on imports from Hungary, where the infection is thought to have originated, would have breached EU rules and provoked retaliation.
Mr Miliband also said there had been a lapse in bio-security allowing bird flu disease to get from Hungary to the UK.
The Tories said ministers should have got a voluntary ban on imports sooner.
Currently EU rules mean Hungary cannot export any poultry from a 10km zone around the place where bird flu has been detected, but anybody outside the zone can continue to trade.
Bernard Matthews, which owns the plant where bird flu broke out in the UK, said on Thursday it had voluntarily suspended all movements of its poultry products between the UK and its plant in Hungary.
However, the company is reported to have imported turkey from the country in the days after the outbreak, despite the government suspecting Hungary was the source of the disease.
Bernard Matthews has insisted it has done nothing wrong and has not brought in turkey from the infected area of Hungary.
Last month bird flu broke out at a goose farm in the south of Hungary.
UK virus expert Professor John Oxford suggested that the virus may have spread to Britain because a single abattoir handled both the infected geese and the turkeys destined for Suffolk.
Hungarian officials say it is just as likely that wild birds brought the virus to Britain.
Mr Miliband told BBC1's Sunday AM a ban on imports would have been illegal.
"That would be in contravention to the EU free trade rules," he said.
"If we had done that, the EU would have taken a very dim view of what we had done and may well have taken measures against us."
But he added that he would have taken moves to restrict imports had he been advised to by vets on public health grounds, irrespective of EU rules.
"First of all, the vets didn't say that for public health reasons that was a sensible thing to do," he said.
1 Feb: Vets called to Bernard Matthews farm in Suffolk after turkeys die
3 Feb: Vets confirm H5N1 strain
5 Feb: Environment minister says most likely cause is from wild bird, but other possibilities being investigated
8 Feb: Government vet suggests turkey meat from Hungary may be to blame. Bernard Matthews denies link
9 Feb: FSA examines whether infected meat may have entered food chain
"And secondly, there will be poultry farmers around Britain saying 'hang on, if there's an outbreak in Suffolk, why should I be penalised outside that area?'"
Peter Ainsworth, the Conservative spokesman for rural affairs, told BBC News the government should have got a voluntary ban from Bernard Matthews on imports "much earlier than happened".
Chris Huhne, the Liberal Democrat environment spokesman, said the government's failure to ban poultry imports from Hungary was "extraordinary".
He added that David Miliband now appeared to have given incomplete answers to the House of Commons in his latest statement, which was made on Monday.
In that statement he told the House the infected UK birds "all came from within this country, so there is no Hungarian connection of that sort".
Professor Oxford said he was "surprised" the government had not banned turkey imports from Hungary.
Mr Miliband also told the Sunday AM programme that Bernard Matthews had been working with the government and added there had been a lapse in bio-security.
He said: "There's obviously been a lapse in bio-security because the poultry has got from Hungary to the UK - to this processing plant - and secondly it's got from the processing plant to the turkey sheds."
Animal welfare minister Ben Bradshaw said the company could be prosecuted if an investigation found that it had broken animal health laws.
The Food Standards Agency is continuing to investigate whether infected products are on shop shelves, and has said a recall is possible if evidence of contamination is found.
The H5N1 virus does not pose a large-scale threat to humans, as it cannot pass easily from one person to another.
But experts fear the virus could mutate at some point in the future and trigger a flu pandemic, potentially putting millions of human lives at risk.