Morrisons is investigating a major breach of its payroll systems after pay and bank account details of about 100,000 staff, from director level downwards, appeared on a website.

The Bradford-based supermarket group was alerted to the leak of data by the Telegraph & Argus which was anonymously sent a disc containing the information by a “concerned Morrisons shopper”.

Morrisons described the leak as a “serious theft of data” and said it was urgently reviewing its internal data security measures.

In a statement today, the company said: “This data theft included bank account details. Morrisons immediately ensured it was taken off the website.

"Initial investigations suggest that this theft was not the result of an external penetration of our systems.

“We can confirm there has been no loss of customer data and no colleague will be left financially disadvantaged.

“We have already informed our colleagues about the theft and we are helping them take the appropriate actions to safeguard their personal data.”

Morrisons said chief executive Dalton Philips was leading the response to the theft and action taken included working with cyber crime authorities and the police to identify the source of the theft.

Experts have been brought in to help Morrisons staff ensure they are not financially disadvantaged, banks have been informed of the matter and a staff helpline set up.