Samples of ice tested from the chains were found to contain the bacteria known as faecal coliforms
Seven out of 10 samples of Costa ice were found to be contaminated with bacteria found in faeces, according to a probe conducted by the BBC's Watchdog programme, to be screened tonight.
At both Starbucks and Caffe Nero, three out of 10 samples tested contained the bacteria.
Expert Tony Lewis, of the Chartered Institute of Environmental Health, said these kinds of bacteria were "opportunistic pathogens - the source of human disease." and warned that the levels found were "concerning".
He said: "These should not be present at any level - never mind the significant numbers found,"
Costa said it had updated its ice-handling guidelines and was in the process of introducing new ice equipment storage.
A spokeswoman said: “We were disappointed with the findings, especially as these stores are all rated Very Good with the top Hygiene Rating of 5. It is extremely important to us that all our stores operate to high standards of hygiene at all times and we take it very seriously when any store fails to meet these standards. We adopt industry standard cleaning processes across all our stores, in line with the Food Standard Agency’s advice. Following these results we have taken immediate action to update our ice handling procedures.”
Starbucks said it was now conducting its own investigation into the claims and said the chain took hygiene "extremely seriously".
A Caffe Nero spokesman said "a thorough investigation" was under way, and that the chain would take "appropriate action".