The BBC claims to have discovered serious breaches of meat hygiene regulations at Welsh abattoirs following an undercover TV investigation.

Journalists posed as veterinary students to carry out the investigation which claims that Meat Hygiene Service inspectors approved carcasses at three abattoirs which were contaminated with faeces.

There is no suggestion that the meat reached the public but supermarkets are examining hygiene practices at a number of Welsh abattoirs including Cig Calon Cymru and Dunbia.

Marks & Spencer and Somerfield are among customers of Cig Calon Cymru, a leading supplier of Welsh Black beef.

Owner Enzo Sauro said the company had consistently met all standards required by regulators, including stringent hygiene regulations.

“We are confident we comply with all regulatory requirements and adhere to best practice at all times,” he said in a statement.

M&S told the BBC that its auditing process meant it was able to fully investigate the concerns raised by the programme, to be shown tonight (October 23).

“We were able to act immediately to carry out a full investigation into the BBC allegations, which showed that our supplier is operating to the standards we demand,” a spokesman said.

Somerfield confirmed it suspended supplies of beef from Cig Calon Cymru and launched its own investigation, as well as issuing a product recall to customers.

Dunbia, which supplies Sainsbury’s, insisted that the latest MHS audit had found satisfactory performance throughout the plant but said it would investigate the allegation.

A third abattoir, HMD, said it supported meat inspectors and wanted them to draw any contamination to its staff’s attention.

Faecal contamination can contain the potentially lethal E coli 0157 food poisoning bug.

The programme has led to a call for an investigation into how the Meat Hygiene Service (MHS) polices the industry.

Professor Hugh Pennington, who chaired the investigation into the 2005 E coli outbreak in Wales, said he was very disappointed with what the undercover journalists claimed to have found.

“We are very good at learning lessons, but we are even better at forgetting them,” he said. “We seem to be going backwards rather than forwards.”

“What we need to do is make sure the rules we have are followed.”

Jane Downes, the veterinary and technical director of MHS, said she had launched an investigation into the BBC’s allegations.

She said she was “quite satisfied” that the majority of controls were perfectly satisfactory, though there were “one or two areas of concern”.

Week in Week Out will be screened tonight (23 October) at 8.30pm on BBC Wales.