Stolen, an M&S laptop containing the pension details of 26,000 staff

Marks & Spencer denied yesterday it had tried to cover up a reprimand over the theft of a laptop containing the pension details of 26,000 staff.

The computer, stolen from the home of a data-processing contractor, was not encrypted or password-protected.

An enforcement notice issued by Information Commissioner Richard Thomas, confirming that M&S had breached the Data Protection Act, reveals: "M&S have concluded they are only prepared to provide undertakings on condition they are not made public, which is not acceptable".

A spokesman for Mr Thomas said: "We always publish the undertakings."

A spokesman for M&S, which has been told to encrypt all its laptops, said: "It was never our intention to cover this up. We did not want to cause undue worry to our staff."