The Health Protection Agency said last night that 31 people in England and Wales have now suffered food poisoning from this strain, known as SmvdX07, since March 1. The most-affected group are 2-year-olds.

While the strain has the same genetic footprint as in the seven Cadbury’s product lines, health chiefs have been unable to establish a direct link between human cases and any particular food.

Alarm bells started ringing on May 22 when the agency realised that there was an upsurge of this food poisoning. It also noted a spate of cases of the same strain in Spain, France and the Netherlands which has particularly affected 6-year-olds, but numbers are in line with usual incidence of the bacterium and so there has been no public health alert in those countries.

Testing of all Cadbury’s chocolate products manufactured in Britain has been stepped up. Trading standards officers in Herefordshire and Birmingham, where the company’s headquarters are situated in Bourneville, are compiling evidence with a view to a possible prosecution.

Cadbury has decided to make no further comment on the issue until the investigations are complete. It insists its products are safe and any risk to human health is minimal.

But the company is clearly facing a backlash in other countries after it admitted keeping silent for five months about salmonella contamination at its factory in Yarbrook, Herefordshire. It first discovered the food bug in January.

In a separate move last night, the agency reiterated its warning to food manufacturers that all ready-to-eat foods on sale, including sweets, should be free from salmonella and its presence even in small amounts “results in such foods being of unacceptable and potentially hazardous quality”.

Cadbury is also recalling all 250g bars of Cadbury’s Dairy Milk Turkish and Caramel bars in the Irish Republic.

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