I am very pleased by the direction that they are now taking

Kenneth Clarke Tory ex-chancellor

In an interview with The Sunday Telegraph, Mr Clarke praised his former competitor's commitment to the poor and vulnerable during a speech to the Conservative's spring conference in Harrogate.

But while he ruled out joining the Tory frontbenches, Mr Clarke offered to give advice on policy matters "to anyone who thinks my advice is worth listening to".

The pro-euro MP for Rushcliffe's comments are marked in their contrast with the leadership challenge seven months ago, during which he described Mr Duncan Smith as a "hanger and flogger" on the BBC's Jimmy Young programme.

'Welcome start'

At the time Mr Duncan Smith claimed Mr Clarke had conducted a "campaign of vilification and smears" and accused him of "verbal abuse".

Mr Duncan Smith beat Mr Clarke by 155,933 votes to 100,864.

Mr Clarke has said in the past that he was "disappointed", but not "totally surprised", to have lost the contest.

But his support of the Tory leader is likely to be seen as a significant personal boost to Duncan Smith's One Nation Tory ideal, which does not have full party support.

Duncan Smith: Follows a One Nation Tory ideal

Mr Clarke told The Sunday Telegraph: "I am very pleased by the direction that they are now taking.

"I thought that the Harrogate speech was a very welcome start to what will be a very long haul to get back into power.

"I think that we lost the general election because we spent the whole time talking about the wrong subjects and adopted a far too strident and extreme tone.

Policy adviser?

"It's extremely important that we talk about the public services and demonstrate that we have 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."

Mr Clarke has promised to "shut up" about the euro unless a referendum is called on whether Britain should join.

I can say frankly that I was horrified by the speech that William Hague gave at Harrogate last year

Kenneth Clarke Tory ex-chancellor

He said he enjoyed the freedom of speech backbench life gave him, but indicated that he would like to take part in policy-making at the next general election.

"I do enjoy policy-making.

"If people want my advice on subjects where I can be helpful - the NHS, the economy, home affairs, what we need to do to make ourselves more business-friendly again - then I am very happy to give it.

"I have no desire to join the shadow cabinet. But my morale as a backbencher is greatly improved when the front bench start doing things that I agree with. Harrogate had that effect."

Mr Clarke said he had been "horrified" by the speech given to the party's spring conference 12 months earlier by William Hague, in which he warned that Britain, under Labour, was becoming a "foreign land".

"Now that the election is over, I can say frankly that I was horrified by the speech that William Hague gave at Harrogate last year," he said.

"It was a quite appalling speech and almost seemed that Euroscepticism was being given strong xenophobic overtones."