Widening rift as David trades blows over criticism of Iraq war

you clapping?” She replied: “I am clapping because as you know, I am supporting him.”

Although Shadow Foreign Secretary David Miliband – whose wife Louise was spotted in floods of tears backstage following his own well-received address the previous day – praised the speech afterwards, he was reported to be heading back to London amid mounting speculation that he will not stand for the Shadow Cabinet, a decision he must make by 5pm today.

The incident took the gloss off his brother’s big speech, in which he signalled a clean break from the era of Tony Blair and Gordon Brown as he sought to quell fears he would lead the party in a lurch to the left after defeating David Miliband courtesy of union backing.

He said the party must “always stand up for the mainstream majority” and fight for the centre ground, but criticised swathes of New Labour’s record including on Iraq, City regulation, immigration, tuition fees and Gordon Brown’s hubristic claim to have abolished boom and bust.

In a bid to ease fears he was in hock to the unions, he called for an end to “overblown rhetoric about waves of irresponsible strikes” saying he would have “no truck” with such action – but won union applause for supporting protection for agency workers, family-friendly working hours and the living wage. Business groups voiced concern at his attack on excessive pay and support for a banking levy.

On the key issue of the economy, the leader insisted he was “serious about reducing our deficit” and warned Labour had four years to restore its economic credibility. “There will be some cuts the coalition does that we won’t like as a party but we will have to support,” he said.

But he accused the Government of being “irresponsible” in not giving equal emphasis to a plan for growth, and even questioned Mr Camaron “patriotism” by suggesting his drive to eliminate the structural deficit within one parliament risked damaging the country which the next generation will inherit.

“True patriotism is about reducing the debt burden we pass on to our kids,” he said. “But Mr Camaron, true patriotism is also about building an economy and a society fit for our kids to work and live in.”

David Miliband praised the speech, which was warmly received in the conference hall, but the ITS News footage later emerged of his exchange with Ms Harman.

During the leadership campaign, Ed Miliband described going to war in Iraq as a mistake, but his brother has defended the decision.