Ed Miliband dismissed the latest criticisms of his leadership as "Westminster tittle-tattle" today as he promised to make Labour the party of society's "grafters".
Mr Miliband used a keynote speech to launch a twin-pronged attack on both excesses in the boardroom and abuses of the benefit system.
He suggested companies could be required to include a staff representative on their remuneration committees while people who were in work could be given priority in the allocation of council housing.
But after a weekend dominated by reports of unrest among Labour MPs and claims of a continuing rift with his older brother David, whom he defeated for the leadership, he was again forced to defend his own performance as leader.
In response to repeated questions by journalists, he said that such matters were of no interest to ordinary voters.
"Ordinary people up and down this country inhabit a different world. People aren't interested in who said what to whom in the Labour Party," he said.
"I am here because I was elected by my party. The gossip and tittle-tattle of Westminster is irrelevant to most people's lives."
The latest wave of speculation about his leadership was sparked by an unauthorised biography by Mehdi Hasan and James Macintyre which alleges he and his brother were barely on speaking terms after falling out as a result of last year's leadership contest.
David Miliband was forced to issue a statement, insisting that he stood "fully behind" his brother and urging the party to do the same.
Speaking today at a south London community centre, Ed Miliband insisted they talk "all the time" and dismissed suggestions that he lacked his brother's wholehearted support.
"I think that is totally untrue," he said. "The reason David issued the statement that he did is precisely to avoid the sort of nonsense and tittle-tattle that is around."
He received some respite when Tony Blair - who was widely assumed to have supported David Miliband for the leadership - offered his public backing.
"I'm content to give Ed my 100% support. I hope and believe he will do well," the former prime minister told BBC Radio 4's The World At One.
In his speech, Mr Miliband emphasised the need for "responsibility" at all levels of society. People were angry, he said, that their taxes were being used to fund bankers and "some people on benefits who aren't bothering to work".
"For too many people at the last election, we were seen as the party that represented these two types of people," he said.
"Labour - a party founded by hard-working people for hard-working people - was seen, however unfairly, as the party of those ripping off our society.
"If you believe in wealth creation and the welfare state like we do, we must acknowledge the only way to protect both of them is through responsibility. We must be once again the party of the grafters."
In an allusion to Peter Mandelson's famous assertion that he was "intensely relaxed" about people becoming "filthy rich", he said: "We were intensely relaxed about what happened at the top of society. I say - no more."
He called for a boardroom culture that rewarded "wealth creation, not failure" - pointing to the contrasting records of former Rolls-Royce chief executive Sir John Rose, who created wealth and jobs, and Sir Fred Goodwin, who presided over the collapse of the Royal Bank of Scotland.
"At the time the financial crisis hit, Fred Goodwin was being paid over three times more than Sir John Rose. What greater evidence could there be of the failure to link pay and performance in our boardrooms?" he said.
He said Labour was looking at imposing a requirement on companies to include a staff representative on remuneration committees and to publish the ratio of the pay of its top earner compared to its average employee.
On benefits claimants, Mr Miliband said he was not trying to "demonise" people but to reward those people who "give something back" to their communities.
He pointed to the example of Manchester, where people who volunteer or who work or have been good tenants in the past are given priority in the allocation of council housing.
"This approach means that rather than looking solely at need, priority is also given to those who contribute - who give something back," he said.
"It is not about punishing people. It is about rewarding people who do the right thing in their communities."
Employment Minister Chris Grayling said Labour was responsible for the state of the benefits system.
"Labour created a welfare system where work didn't pay, where families were sometimes better off apart and where average earners paid for benefits claimants to live in houses they could never afford themselves."