Chocolate giant Cadbury faces the prospect of legal action and a fine for its failure to tell the authorities immediately that some of its products were contaminated with salmonella.

Yesterday thousands of customers rang the helpline set up by the firm this weekend after more than one million chocolate bars were recalled. Many customers, demanding to know why it had taken the company five months to disclose the danger, found it could take an hour to get through as the company was taken aback by the scale of the reaction.

The Food Standards Agency, which oversees food safety in Britain, has begun an investigation, and lawyers from the FSA and the two local authorities covering Cadbury’s Bournville headquarters and the Herefordshire factory where the infection was found will meet this week to decide whether to prosecute.