The row which resulted in the resignation of Peter Mandelson refused to die down on Sunday with Downing Street suggesting the former minister had become "detatched" in recent weeks.

After a bad week for Tony Blair, the former Northern Ireland secretary stood firm, making clear in a Sunday Times article that he remained innocent of the charges of lying.

"I am not a liar. I did not lie. What I did do was make the mistake of speaking out before establishing all the facts and rushing into last-minute interviews," wrote Mandelson. "This relatively trivial error was turned into a huge misjudgment that led to my resignation."

He also said he had been rushed into making his shock resignation and did not rule out trying a further political comeback. "A small mistake, a failure to focus on a small matter had turned into a monumental disaster," he said. "I know I have a mountain to climb before reversing this error, but I know I have to start somewhere.''

Downing Street on Sunday attempted to calm the affair - denying that Alastair Campbell had tried to rubbish the minister since his resignation - despite earlier reports suggesting Mandelson had not been on the ball in the weeks leading up to his resignation.

The row over the Hindujas' passport applications also refused to go away over the weekend, despite an intervention from the Indian tycoon Srichand Hinduja who said many of the allegations levelled at Foreign Office minister Keith Vaz had been "totally false".

In an interview on the Frost programme Hinduja did, however, admit that he had asked Vaz for information on the rules surrounding British citizenship.

The Tories are still demanding answers from the government. Iain Duncan Smith, the shadow defence secretary, told the Sunday Programme that the inquiry should go further than proposed. "It is time to clean the house, which, I suspect, the prime minister is not very keen to do this close to the election because he may well know that the rot goes much deeper than just one man,'' he said.

Jack Straw, the home secretary, denied that the government would seek to kick the inquiry into the long grass. He told the Dimbleby programme that the report from Sir Anthony Hammond would be published "within weeks" - suggesting it would be made public ahead of the general election.

It has also emerged that it was Straw who put the call in to Number 10 - alerting the prime minister to the discrepancy between Mandelson's account and the actual events.

Mandelson was on Sunday attacked by Labour's former deputy leader Lord Hattersley. "It is obvious that something very strange is going on inside his head. It is very sad, it will do him immense damage, it is a terrible mess, but it is a temporary mess,'' he told the Breakfast With Frost programme.

However, other senior Labour figures have moved to defend Mandelson. The former social security minister Frank Field accused Downing Street of going too far. "Clearly Number 10 is not going to have him back on any terms. Both sides seem to be to be out of control. There is no mercy. I think Number 10 should have laid off," he told the Sunday Programme.