DAVID Miliband has attacked Labour’s failures under his brother’s leadership, saying the party had “turned the page backwards” and needed to return to the policies pursued under Tony Blair.

In an interview with American news channel CNN, the former foreign secretary – who now heads the International Rescue Committee in New York, after narrowly losing out to Ed Miliband in the 2010 leadership battle – again underlined he would not play a role in the party’s current contest.

But, after initially promising a “statesmanlike demurral” to questions about Labour’s defeat in May under the leadership of his brother, Miliband went on to say the party’s electoral collapse had come “for a very clear reason”.

“What I think is important for all the candidates [to replace Ed Miliband] is to reflect on the very clear lessons of two devastating electoral defeats for the Labour Party in the last five years, which have come for a very clear reason. And the reason is that the public have concluded that instead of building on the strengths and remedying the weaknesses of the Blair years, the party has turned the page backwards rather than turning the page forwards.”

The answer to this, Miliband said, was for the party “to find again that combination of economic dynamism and social justice that defined the success of the Labour Party” under Blair.

His comments follow more guarded statements made in the immediate aftermath of Labour’s election defeat in which he said he hoped in the near future to be “freer to contribute” to the debate about where the party went wrong.

In a separate interview with the Times, Miliband said his “worst fears were confirmed” when his brother led Labour to its most comprehensive defeat in 30 years. He added: “I had spent the previous two or three weeks wondering whether in fact I was wrong to believe that you couldn’t suspend the laws of political gravity because the polls obviously suggested that things were close, but ... the politics of our offer and our positioning made me very fearful of the consequences, and that was borne out.”

He said that the defeat was “doubly painful” because of his brother’s involvement.

“I don’t want him hurt and I don’t want him to be vilified,” he said. “There is no consolation in any sense of vindication, frankly, because I care about the country and I care about the party.”

On the forthcoming referendum on EU membership, Miliband said Labour should argue that “even the talk of Britain leaving the European Union is dangerous for Britain, and the reality would be disastrous”.

He added: “Sitting in New York, it’s completely evident to me that no American government would ever take seriously a Britain that has withdrawn from the European Union. It’s almost like Britain would be resigning from the world.”

Labour would need to be at the forefront of the campaign to remain in the EU, despite not being in government, he said.

Contrary to the assertion by acting leader Harriet Harman this week that some Labour voters had been “relieved” that the party was not in government, Miliband told CNN he thought there was a “profound sense of shock and disappointment in Labour ranks”.

And he implied that Labour under his brother’s stewardship had not been trusted on the economy, saying the party “needs to catch up with the way Britain has changed, the way politics has changed, and the kind of agenda that needs to be set in an age of economic insecurity”.

Three of the contenders for the Labour Party leadership have now reached the 35 nominations from MPs required to secure a place on the ballot.

Andy Burnham, Yvette Cooper and Liz Kendall have met the target; Jeremy Corbyn has 11 backers, and Mary Creagh has five. Nominations close on 15 June.