David Miliband has said it would have defied "political gravity" for his brother Ed Miliband to have won the general election last month.
The former foreign secretary, who lost the Labour leadership race in 2010 to Ed, has used two separate interviews to criticise his brother.
In an interview with CNN's Christiane Amanpour on Tuesday evening, David Miliband, who is currently head of the International Rescue Committee charity in New York, was initially questioned about foreign policy. When Amanpour switched topics to British domestic politics and Labour's election defeat, Miliband said he would respond with a "statesmanlike demurral".
However he quickly went on to say: "What I think is important for all the [Labour leadership] candidates 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."
Miliband added: “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."
"I think its responsibility of all the candidates to find again that combination of economic dynamism and social justice that defined the success of Labour Party in 1990s and early 2000s."
In a separate interview with The Times today, David Miliband said: "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."