Bernard Matthews, the company at the centre of February's bird flu outbreak at one of its turkey farms in Norfolk, will not face prosecution.

A Food Standards Agency investigation had been examining the possibility that food waste at the site may have been stored inappropriately.

However, the FSA said the investigation had found no evidence that the company had breached by-product or food hygiene regulations.

“We have carefully scrutinised and considered the evidence in this case and concluded there is insufficient evidence to provide a realistic prospect of conviction,” the FSA said in a statement.

“Accordingly, we have carefully decided not to proceed to a prosecution in this case.”

The Liberal Democrats described the FSA's decision as “astonishing” while the Conservatives said it was “entirely clear” there were breaches of biosecurity, according to reports in the Guardian.

Bernard Matthews welcomed the decision: “Bernard Matthews has always maintained that it has acted with the utmost integrity and co-operated fully with the authorities,” a spokesman said.