Aide will 'tell all' on IDS wife

The heat on Iain Duncan Smith increased dramatically today as the woman official at the centre of the Betsygate affair vowed to "tell the truth, no matter what the cost".

Vanessa Gearson's comments appeared to signal she thinks her evidence will be highly damaging to his fight to clear his name of misconduct.

It emerged she is preparing to testify to the inquiry headed by standards watchdog Sir Philip Mawer - and will give both oral evidence and documents, thought to be emails and internal memos.

In another twist, two other senior Tories were expected to give evidence to Sir Philip's investigation into claims that Mr Duncan Smith paid his wife Betsy for work she did not carry out. Mark Macgregor, former Tory chief executive, will, if asked, give evidence to the standards commissioner. Stephen Gilbert, the campaigns director at Tory HQ, was also said to be willing to answer any summons from Sir Philip. All three are thought to believe Mrs Duncan Smith did little work in return for her £15,000 salary.

Dr Gearson today broke cover to talk to the local paper in Cheltenham, where she is standing at the next election - and made clear she is unafraid to cause embarrassment for her leader.

"I don't believe the people of Cheltenham would wish for me to do anything other than to tell the truth and to stand up for my principles, no matter what the cost," she said.

Her email in January warning of a "Crick-style investigation" into Mrs Duncan Smith's payments triggered the storm.

Mr Duncan Smith denied the charge that his wife had been paid taxpayers' money for secretarial work she never performed. He lashed out at the "cowards in the shadows" in his own party leaking misinformation about his wife in order to sabotage his leadership.

Sir Philip stressed that the fact he was extending his initial inquiry did not mean there was conclusive evidence one way or the other but that the claims put before him, many of them anonymous, made further inquiries unavoidable.

Sir Philip also called for the leakers to declare themselves, warning: "People who want to make serious allegations against an MP or, indeed, anybody else, have got to be prepared to put up or shut up."

Mr Duncan Smith, on the rack as never before, survived one Commons test in a Prime Minister's question time confrontation with Tony Blair.

Tory chief whip David Maclean moved this afternoon to crack down on rebel MPs. He threatened disciplinary action against a small group, thought to include Nick Gibb, the MP who accused Mr Duncan Smith of being " incoherent" during last week's party conference.