Clarke gives Tory leader his seal of approval

Kenneth Clarke, the defeated Tory leadership contender, has personally endorsed Iain Duncan Smith's stewardship of the party.

Mr Clarke said he was "surprised and delighted" at Mr Duncan Smith's commitment to the vulnerable, praising his speech at the party's spring conference in Harrogate.

In a significant show of solidarity with the new leader, Mr Clarke pledged to "shut up" about the single currency unless a referendum on the euro was called – a move which may go some way to healing the Tory rift on Europe. And he hinted he would be prepared to become an informal adviser to the party on policy, in particular its bid to appeal to business leaders. But, he said: "I have no desire to join the shadow cabinet."

During last year's leadership contest Mr Clarke branded Mr Duncan Smith a "hanger and flogger". Six months later, however, he told The Sunday Telegraph: "I am very pleased by the direction that they are now taking."

The Harrogate speech appears to have been the catalyst for Mr Clarke's change of heart. "It's extremely important that we talk about the public services and demonstrate we have a genuine concern for the vulnerable and less well-off people. But this will have to be followed up and have some substance put on it.

"It will take more than one weekend to persuade people that the Conservative Party is heading back in a more sensible direction."

The former Chancellor was much less generous in his comments about the last Tory leader, William Hague, saying the 2001 general election had been lost because the Tories talked about the wrong subjects and took a "far too strident and extreme tone".

Contrasting Mr Duncan Smith's speech in Harrogate with Mr Hague's performance in the town a year earlier – the controversial attack on Labour, accusing the government of turning Britain into a "foreign land" – Mr Clarke said he was "horrified" by Mr Hague's remarks. "It was a quite appalling speech and almost seemed that Euroscepticism was being given xenophobic overtones."