Tony Lewis, Chartered Institute of Environmental Health, told the programme: "The level of contamination of faecal bacteria concerns me a great deal.

"The bacteria found are opportunistic pathogens - the source of human disease. These should not be present at any level - never mind the significant numbers found."

Cleanliness of tables, trays, and high chairs at the chains was also tested at 30 branches.

A Starbucks spokesman said it takes hygiene "extremely seriously" and "nothing is more important" than customer safety.

"We have moved quickly to conduct our own investigation into the claims about the stores," he added.

"All employees nationwide have received updated training on our high standards of hygiene including ice handling."

Costa said: "We were disappointed with the findings, especially as these stores are all rated 'very good' with a the top hygiene rating of five.