Mr Mandelson resigned on Wednesday after he failed to declare a £373,000 loan, obtained as part-payment for his Notting Hill home, from a fellow minister, Paymaster General Geoffrey Robinson, who also resigned.

Tony Blair: Peter made a mistake

In an interview with BBC Radio 4's Broadcasting House, broadcast on Sunday, the prime minister sought to limit damage from the scandal by saying that New Labour was "bigger than any individual".

"What is important now is that we keep a sense of perspective about it," he said.

Tony Blair: The government's work goes on

"There will be a certain number of people who will be foolish enough to think that Peter's going means that somehow there's some blow to the project of New Labour.

"That goes on. We got elected as New Labour - we'll govern as New Labour."

But the Conservative deputy leader Peter Lilley accused the prime minister of failing to condemn wrong-doing.

He told the BBC: "It is not possible for the prime minister to brush this aside as if his cronies do not have any rules applied to them that apply to everyone else."

As Mr Blair spoke, Sunday's newspapers unveiled a wealth of new allegations against the Labour politician already said to be considering a rapid comeback.

BBC Political Correspondent Emma Udwin: The prime minister may be trying to distance himself from Mandelson

The Sunday Mirror claims that Mr Mandelson had an unknown £100,000 mortgage at the time he purchased his house.

It questions whether Mr Mandelson declared the mortgage to the Britannia Building Society. He has already been asked whether or not he declared Mr Robinson's loan when he applied for a £150,000 mortgage from the Britannia - as required by law.

Tony Blair: No blow to New Labour

A spokesman for Mr Mandelson said that no comment would be made until he had received a copy of his mortgage application form from the Britannia.

Meanwhile, The Express on Sunday says that Mr Mandelson failed to declare a free trip he took as the guest of American millionaire businesswoman Linda Wachner in the House of Commons Register of Members' Interests.

Peter Mandelson: Undeclared flight

A spokesman confirmed that the former trade secretary had not declared the flight, but said that it was undertaken in a "personal capacity" and was "nothing to do with the DTI".

Tory Shadow Chancellor Francis Maude said the gift was a "clear breach" of Parliamentary rules.

"We will be asking the Parliamentary Commissioner for Standards to investigate this matter.

Brown 'bankrolled'

"We will also be pressing the prime minister for a full investigation into decisions taken by Peter Mandelson as Trade and Industry Secretary to ensure that no impropriety has occurred," he said.

Geoffrey Robinson: "Funded" Gordon Brown's office

Pursuing the former paymaster general, The Sunday Telegraph, The Observer and the Independent on Sunday allege that Mr Robinson "bankrolled" Chancellor Gordon Brown's office and subsidised his staff in the run-up to the 1997 election.

The Sunday Times says that Mr Robinson offered three other unnamed ministers "help" in relocating to London and implicates Mr Brown's press secretary, Charlie Whelan, in the negotiations.

The BBC's Christine Stewart: "Mr Blair stresses the government will go on"

The newspaper says it was part of a scheme to build up support for the chancellor as Mr Blair's likely successor as party leader.

A senior Treasury source described the claims as "completely and unequivocally untrue". He added: "This story is baseless and malicious."

On Saturday a spokesman for the former trade secretary had asked the media to stay away. He said: "He... hopes the media will respect his need for time off."