Earlier this month, it was revealed that the Revenue had deleted an unknown number of taxpayer records as part of routine 'housekeeping' of its PAYE computer.

However, Baroness Noakes's statement attaches a figure to the software error that looks like becoming another embarrassing IT disaster for Whitehall.

Ministers are expected to reveal just how many people have been affected by the problem within the next fortnight.

Lord McIntosh of Haringey said the error that caused the deletions had been corrected, and claimed it affected only 'a small minority' of taxpayers.

The Inland Revenue has 250 major IT systems and 3,000 staff working in IT. It produces 170 million forms per year and runs 100,000 desktops.