Ed Miliband's leadership is under increasing pressure after a slew of negative polls and comments from former New Labour stalwarts.
The Labour leader's popularity is now at its lowest, behind even Nick Clegg, who was previously seen as the barometer of unpopularity.
A YouGov poll on Thursday found that 60% of voters think Mr Miliband is not up to the job of prime minister - of those 43% were Labour voters.
The survey for Prospect magazine also found more people thought Mr Miliband's brother, David, would make a better premier.
An IPSOS Mori poll for the Evening Standard yesterday found 49% of voters thought Mr Miliband should be replaced.
Former cabinet minister Lord Mandelson failed to back Mr Miliband firmly saying he was the "leader we have".
Alan Johnson, former home secretary, further highlighted Mr Miliband's unpopularity by saying the Labour leader was not a hit on the doorstep.
Speaking as he unveiled a new tough policy on benefits , Mr Miliband said he was happy he could "defy the odds" and win next year's election.
He said he would not provide "continuity Labour" and said he was happy to listen to the advice of people like Lord Mandelson, but added that while the 2015 election would be a tough fight, he was determined to win.
The results of the poll will, however, make worrying reading for the Labour party just a year out from the General Election.
Mr Miliband suffered a gaffe-prone local and European election campaign, forgetting the name of the Labour Party council leader he was campaigning for in Swindon and failing to get a handle on his shopping bill.
He was also mocked over unflattering pictures of him eating a bacon sandwich.
And more recently he apologised for posing with the copy of The Sun to promote its World Cup edition.
Asked on the BBC's Newsnight whether Mr Miliband was the best leader for the party, Lord Mandelson said: "In my view he is the leader we have and therefore the leader I support, and somebody who I believe is capable of leading the party to victory."
He said: "What Ed is trying to do is approach politics in a rather different way from the way in which Tony Blair and New Labour approached it.
"It may work. It may well be successful. I would say to you that electoral arithmetic is probably on his side."
He said the leader had some good policies but had failed to win through with his personality and needed to create a "convincing vivid narrative" about what he stood for.
Alan Johnson told the New Statesman magazine the Labour leader was "not as able to connect (with people) as strongly" as his brother David.
He said: "It's not his strong point I can't pretend that, knocking on doors, people come out and they're really enthusiastic about Ed."