Tories pile pressure on Darling

The Treasury indicated the Chancellor had no immediate plans to make a second statement to MPs on the crisis at HM Revenue and Customs, as demanded by his shadow George Osborne.

But it is thought likely that the Tories will ask Speaker Michael Martin to order Mr Darling to the despatch box to answer an urgent question, after they accused him of failing to provide "the whole truth" about how two discs containing personal details of 25 million people went missing in the HMRC's internal mail system.

Data protection minister Michael Wills will face a grilling on the blunder when he gives evidence to the cross-party Joint Committee on Human Rights in Westminster.

Meanwhile, police continue to search premises of private courier company TNT, which operates the HMRC internal mail system, for any sign of the missing discs.

Senior ministers have been forced to defend the Government's competence, as a slew of polls suggested the HMRC affair had inflicted significant damage on its reputation for being able to handle a crisis.

Justice Secretary Jack Straw dismissed as "utter nonsense" suggestions that the problem was Labour's Black Wednesday, and insisted Prime Minister Gordon Brown was a "very good crisis manager".

The Prime Minister himself insisted that problems at HMRC and ailing bank Northern Rock were caused by factors outside the Government's control, and urged voters to judge him on his long-term record of delivering economic stability.

Opposition parties questioned Mr Darling's assurance, in a statement to Parliament last Tuesday, that the discs went missing solely due to the actions of a junior child benefit official in Washington, Tyne and Wear, who breached procedures by sending them to the London HQ of the National Audit Office.

Shadow home secretary David Davis said it was "at best ignominious and at worst dishonourable" to try to pin the blame on a single member of staff, when e-mails released by the NAO suggested that more senior officials were aware of the arrangement.