Former Labour leader Lord Kinnock has rallied to the defence of Ed Miliband, praising his “great personal and political courage”.
Mr Miliband’s leadership has come under intense scrutiny, but he has insisted he can defy the odds to win the next general election.
Lord Kinnock insisted that Mr Miliband is a “real leader” and said he has the “toughness” to take the party into government.
Mr Miliband has had low personal approval ratings in a series of opinion polls, with one recent survey finding that voters thought his older brother David would make a better prime minister.
In an interview with The Observer, Lord Kinnock, who backed the younger Miliband’s leadership bid, hit out at the “vindictiveness” of the press.
Lord Kinnock said Mr Miliband faced “a hostile press which thought he was a soft target and have not forgiven him for proving them wrong”.
But he added: “It won’t stop him; his genuine strengths of thought, action and toughness will get through and help to win victory.”
The former leader said: “Ed has great personal and political courage. The way in which he’s taken on (Rupert) Murdoch, big energy, banks, and effectively prevented our military engagement in Syria shows that. He’s got high intelligence and articulates deep concerns.”
An Opinium poll in the newspaper gave Labour a four-point lead over the Tories, with Mr Miliband’s party on 35 per cent, the Conservatives on 31 per cent, Ukip on 17 per cent and the Liberal Democrats on 7 per cent.
But, in an indication of the challenges facing Mr Miliband, just 23 per cent of the electorate said they approve of the way he is handling his job as Labour leader, compared with 49 per cent who disapprove.
David Cameron had better ratings, with 37 per cent approving of his performance as prime minister against 47 per cent who disapprove.
Shadow business secretary Chuka Umunna said Mr Miliband was a “man of great beliefs” and dismissed concerns about his poor personal ratings.
Opinium carried out 1,946 online interviews from June 17 to 19.