Iain Duncan Smith: 'Cameron needs the room to fail occasionally without the whole party turning on him'

One of the more excruciating spectacles of the decade was Iain Duncan Smith ­ whom many people saw as a decent man out of his depth ­ declaring, with artificial ferocity, during his leader's speech to the 2003 Conservative conference: "The quiet man is back, and he's turning up the volume."

It was, of course, enemies within his own party who turned up the volume, and soon the quiet man was on the back benches, where he has quietly remained.

He may not qualify as a big beast in the political jungle, but he is one of the few who could tell David Cameron, from personal experience, what it is like to lead the Conservative Party.

"It's like nothing else you have ever done," he said, talking volubly in the incongruous setting of Don Miguel's Tapas Bar by Chingford station in Essex. Here, in the constituency that he has represented for 13 years, the notorious frog that infested his throat when he tried to take on Tony Blair in Prime Minister's Questions does not trouble him once.

"Even though you guys have witnessed it, I have to tell you that until you've experienced it, you have no idea what it's like. When you're rebuilding a party, when you're trying to get it focussed on winning elections when the spirit is low and morale's not great, that's your toughest time. The difficult times were when the backbiting started. But there are fantastic times too."

He voted for Mr Cameron last week, and shares the general expectation that he will be tomorrow's winner. He is adamant that the new leader must be shown loyalty that neither he, nor his predecessors, William Hague and John Major, ever enjoyed.

But he is not making trite comparisons between Mr Cameron and Tony Blair. He does not believe that the Tories are as disciplined a political army as that which Blair inherited in 1994, or that Cameron is a "Prime Minister designate" in the way Mr Blair so obviously was. He is not predicting the outcome of the next election, but he sees Mr Cameron as a gifted leader who is learning fast, but with a long road ahead.

"I want David Cameron not to have to put up with what William and I put up with, when every time you want to say something you've got 10 MPs going off and rubbishing what you're saying, which happened to both of us. We can't do that any more, because if we do that, David Cameron is never going to succeed.

"He has to have discipline behind him so that even if we disagree, we must never turn it into an attack on the leader. He's got to develop, like Thatcher developed in 1975 to 1979.

"And when he makes a mistake, and he will make mistakes, and when he fails ­ and he will fail on certain things ­ the test for us is whether we can hold our nerve and say nothing. Just say to the likes of you 'well, can't win everything'.

"Blair said to me when I first saw him, 'you've got the very worst job in British politics' ­ and of course when he had it he was already just Prime Minister designate really, so he did not have anything like the time that most opposition leaders have, like Neil Kinnock, or William or me.

"The real thing that turned Labour was when it finally decided to back its leadership. Since then, the Labour self-discipline has been phenomenal. Even today, when they have real problems with Blair, for the most part it's the usual suspects you hear from. Even when there have been rebellions, the party itself hasn't gone out and had a go at the leadership in the way that we got used to doing.

"That was the big difference for Labour ­ the moment when they said 'we really need power'. That's the big thing I say to my party: you've got to want to be in power."

There have been phases in the political life of Iain Duncan Smith. Party discipline was not top of his agenda when he arrived in the Commons a year and a half after the coup that removed his political heroine, Margaret Thatcher, with whom he is still in touch. He made his reputation as a hardline, anti-EU Thatcherite and as one of the most persistent backbench rebels against Mr Major over the Treaty of Maastricht.

"Do I regret that?" he asks. "I regret that the party was disintegrating, but I think that disintegration was happening anyway. From the moment I came in, in 1992, after the fall of Thatcher, the mood was pretty febrile. But there is a difference between having the argument over an important issue, and briefing against the leader. I never went personal. I never briefed against him."

Then he went through a phase as a loyal member of Mr Hague's shadow cabinet, and as his ill-starred successor. Then he was feeling around, wanting to add a social dimension to a Conservative philosophy which, in the public mind, seemed to consists only of promises of tax cuts, longer prison sentences, fewer immigrants and looser ties with Europe. Now he talks with the fervour of a convert about putting family breakdown and social disintegration at the top of the political agenda. Last year, he set up the Centre for Social Justice, which has built up contacts with voluntary groups working among the socially deprived. He is immensely proud of its location in Lambeth, in the very building from which William Wilberforce campaigned for the abolition of slavery. One reason he voted for Mr Cameron was that he had paid four visits to the centre, compared with David Davis's one.

The man who once believed in hanging is now obsessed ­ if he will pardon the expression ­ with being tough on the causes of crime. His biggest target is the gang culture that draws teenagers into serious crime. He has no doubt that its prime cause is family breakdown.

"These kids that are almost feral. Why? Because they have no families, they have no homes, schools gave up on them, and nobody cares a damn.

"I used to think that as long as the police were arguing for capital punishment, that was a legitimate argument. Now I don't think it works as a deterrent. We have got to get to these guys earlier."

All of this has a political dimension, he is quick to point out. If a Tory wants to cut taxes, one way is to tackle the social problems that make people dependent on the welfare state. A coherent social policy might also solve the Tories' big image problem. "If you are a Conservative and you want to reduce the cost of government, then the growing demand for the welfare state is your number one concern, because this is demand led now. We have no control over it. So it's it time you looked at why the welfare state is growing."

But surely it is also time to ask why the Conservative Party has not been growing for a long time, no matter how much money is poured into it. " We have no narrative in which to set the idea of the Conservative Party," he replied. "We never talk about whose side we're on, who we really care about, we never talk about the breakdown of society because it embarrasses us. What we allow our opponents to do is thereby characterise us as unfeeling, as people who really don't care, which is untrue."

And is Mr Cameron the man with the narrative, whose arrival will be the start of a Tory era? He was not wildly optimistic. "Their self-discipline has been strong. Our self discipline has been non-existent. David Cameron needs the room to be able to fail occasionally without the whole party turning on him.

"We may not win the election," he added. "But we're developing."