The Government is powerless to impose a ban on meat imports unless beef contaminated with horse meat is found to be a health risk, environment secretary Owen Paterson said.

The Food Standards Agency (FSA) has said there is no evidence to suggest the horse meat detected poses a danger to humans, but confirmed that tests have been ordered on products for the drug phenylbutazone as animals treated with "bute" are not allowed to enter the food chain.

Mr Paterson was speaking after warning that the next set of results on all retailers' and manufacturers' processed beef products could reveal further traces of horse meat.

"There may well be more bad results coming through, that's the point of doing this random analysis," Mr Paterson said.

The results, ordered by the FSA, are due on Friday.

Mr Paterson repeated his vow to get to the bottom of the scandal, which he has suggested is part of an international criminal conspiracy.

He said: "This week obviously we'll be talking to counterparts across Europe, because ultimately this is EU competence."

Asked if he would consider a ban if tests proved there was a food safety risk, he added: "If there is a threat to public health that is allowed within the rules of the European market."

Frozen foods firm Findus, which has taken its beef lasagnes made by French food supplier Comigel off shelves after some were found to have up to 100% horse meat in them, said it was considering taking legal action against its suppliers as an internal inquiry "strongly suggests" the contamination "was not accidental".

The scandal has spread all over the continent as details of the elaborate supply chain in the meat industry emerge.

French consumer safety authorities have said companies from Romania, Cyprus and the Netherlands as well as its own firms were involved.

Beef products suspected of containing horse meat have also been withdrawn from shops in Ireland and France.

Tesco and Aldi have also withdrawn a range of ready meals produced by Comigel.