Cadbury is stepping up salmonella testing at the huge plant where contamination occurred, it said yesterday.

It will only release products after the results have come back negative. Any product which tests positive will be destroyed.

The move follows heavy criticism of Cadbury's risk assessment system in the wake of the salmonella chocolate recall.

A group of scientific advisors accused the confectionery giant of using "unreliable" salmonella testing methods.

The Food Standards Agency's independent advisory committee on the microbiological safety of food said Cadbury's method of salmonella risk assessment could not be relied on for foods such as chocolate.

After meeting with the FSA yesterday, Cadbury pledged to thoroughly clean production lines at its plant in Marlbrook, Herefordshire.

The company recalled more than a million chocolate bars across seven product lines after a leaking pipe at the factory caused salmonella contamination.

Cadbury UK managing director Simon Baldry said: "We regret any concern the recent recall may have caused to our consumers. We have always acted in good faith, and we are happy to change our procedures based on advice from the FSA and Environmental Health Officers."

The FSA said in a statement: "Cadbury will increase its sampling and testing to levels that will provide a higher degree of reassurance that contamination would be picked up."