The Labour Party must become a "great reforming movement" that redistributes power and opportunity to enable it to regain the trust of the electorate, David Miliband has said.
The shadow foreign secretary and Labour leadership contender said he wanted the party to become a "fighting force" across the country as it sought to reconnect with the British people.
And he attacked the coalition Government's programme of cuts to curb welfare and reduce public sector pay bills, accusing Deputy Prime Minister Nick Clegg of "breathtaking hypocrisy" in claiming the forthcoming pain would not mark a return to Thatcherism.
Mr Miliband was also pressed on his decision not to resign from the Government and stand against then prime minister Gordon Brown when his Cabinet colleague James Purnell dramatically left the Government last year.
He said: "We all have to take our share of the responsibility but I am never going to make a bad situation worse and that is what I was being asked to do last summer and the summer before."
He also tried to distance himself from his Blairite label, saying he was the "Miliband D" candidate, adding: "I think that it is very important that we have a political process where people define themselves by who they are.
"That is what I am trying to do in this campaign."
Speaking on BBC1'S Andrew Marr Show, Mr Miliband said: "The Labour Party succeeds when it is a movement for change in communities, not just at Westminster.
"What I am saying in my campaign is for the Labour Party to become an effective fighting force at Westminster again is that it needs to be a fighting force right across the country."
He added: "What I think the Labour Party has to do if it is to regain the trust and confidence of people is to become that great reforming movement to redistribute power and opportunity again."