The Opposition warned on Monday that lax quarantine procedures could be putting Britain at risk of an avian influenza epidemic.

Shadow agriculture minister Jim Paice welcomed plans for a review of avian quarantine arrangements and procedures for captive birds.

But he said that the Essex centre at the heart of the latest fears had prompted wider questions over whether other birds may have been infected.

"Whilst a review of quarantine rules and procedures is necessary it must not obscure the urgent questions surrounding birds which may have been in the quarantine centre in Essex," he said.

"The fact that Margaret Beckett has not taken this opportunity to provide further information or answers shows that Defra really does not understand how serious the situation is."

Paice urged the government to "explain if any birds shared the premises whilst the parrots and the birds from Taiwan were present".

"If they did, what efforts are being made to trace them?" he asked.

"Has contact been made with cage bird clubs, societies; show and fair organisers, magazines and journals? 

"Have Defra contacted environmental health officers in local authorities?

"Has Defra considered offering amnesty if necessary to encourage anyone to report buying or selling these birds?

"If the stories that other birds went through the quarantine centre at the same time are untrue, then the government should say so."

The environment secretary, meanwhile, detailed the terms of reference for the independent review of avian quarantine arrangements.

Beckett said: "I recognise that the public is concerned about avian flu. As a result of existing quarantine procedures disease was identified and eradicated in a quarantine facility in Essex.

"However, we want to ensure that in this evolving disease situation our quarantine rules and procedures are as secure as possible.

"That is why we want an independent assessment of the quarantine system's effectiveness against avian flu.

"The importation of wild birds is currently suspended and all birds currently in quarantine are being assessed on a case by case basis. This review will be carried out during that suspension."