Earlier this year Europe's horsemeat scandal revealed how processed meat can get mislabelled in a complicated supply chain.
Waitrose also withdrew a number of products when the horsemeat scandal came to light.
Scottish Liberal Democrat rural affairs spokesman Tavish Scott said the horsemeat scandal was completely unacceptable.
But it has been sorely tested by the horsemeat scandal, which broke last month.
Ireland has called a meeting of EU officials from countries affected by the horsemeat scandal.
On Wednesday, DUP MEP Diane Dodds described the horsemeat scandal as one of "mammoth proportions".
BBC: Burgers recalled from NI schools are 'clear of horse DNA'
Food sales were up by 1%, despite the horsemeat scandal which threatened to affect the big supermarkets.
BBC: UK retail sales grew at fastest rate for years in February
The environment secretary has welcomed plans for EU-wide, random DNA tests to tackle the widening horsemeat scandal.
Beef has been removed from school meals across Staffordshire as a precautionary measure amid the horsemeat scandal.
Mr Clarke said his supermarket would work more closely with British farmers in response to the horsemeat scandal.
Meanwhile the environment minister Owen Paterson is meeting with retailers and the FSA to discuss the horsemeat scandal.
She said the cost of West Country beef had also risen because the horsemeat scandal had increased consumer demand for beef.
The leader of Scotland's farmers has said the industry feels angry and betrayed by big retailers following the horsemeat scandal.
BBC: Scots farmers 'angry and betrayed' by horsemeat scandal
More than half of UK consumers have changed their shopping habits as a result of the horsemeat scandal, a consumer group survey suggests.
The discovery comes as European Union agriculture ministers meet in Brussels for talks widely expected to focus on the horsemeat scandal.
Tesco has apologised after burgers that were withdrawn in the wake of the horsemeat scandal were found on sale in Oxfordshire.
Environment Secretary Owen Paterson will travel to Brussels on Wednesday for a meeting of European countries caught up in the horsemeat scandal.
The horsemeat scandal began last month when Irish authorities discovered horsemeat in some burgers stocked by a number of UK supermarket chains.
The council's Scientific Services has been carrying out the tests to check meals are of the required standard following the horsemeat scandal.
The FSA has lifted its suspension of the Peter Boddy slaughterhouse in Todmorden, West Yorkshire, raided in the wake of the horsemeat scandal.
Retailers should "take a more proactive role" to reassure customers that food is safe in the wake of the horsemeat scandal, he said.
The news comes after Mr Paterson met with supermarket executives to discuss how to restore consumer confidence in the wake of the horsemeat scandal.
The FSA said it was the first time bute had been found in a meat product in the UK since the horsemeat scandal started.
Newport council has become the ninth local authority in Wales to withdraw certain meat products supplied by a firm caught in the horsemeat scandal.
Farmers' anger at the horsemeat scandal will be reflected at the national conference, NFU leaders have said - which is being held in Birmingham.
It follows the news on Thursday that beef is being removed from school meals across Staffordshire as a precautionary measure amid the horsemeat scandal.
Northern Ireland's farmers feel angry and "badly let down" by the ongoing revelations in the horsemeat scandal, the Ulster Farmers' Union (UFU) has said.
Earlier on Wednesday, Tesco announced it was dropping Silvercrest, part of the ABP Food Group, as a supplier in the wake of the horsemeat scandal.
"The horsemeat scandal exposed the need for urgent changes to the way food fraud is detected and standards are enforced, " said Which? executive director Richard Lloyd.
If the horsemeat scandal encourages people to eat fewer meals of mass-produced burgers, lasagne and bolognese, it would be one positive outcome from this unpleasant scandal.
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