03/07/2014 20:10 BST | Updated 04/07/2014 04:59 BST

Ed Miliband Is A Winner, Sadiq Khan Tells Critics Of Labour Leader

ADRIAN DENNIS via Getty Images
Sadiq Khan, British Shadow Secretary of State for Justice and Shadow Lord Chancellor, delivers his speech during the final day of the Labour party conference in Brighton, east Sussex, south England, on September 25, 2013. AFP PHOTO / ADRIAN DENNIS (Photo credit should read ADRIAN DENNIS/AFP/Getty Images)

Ed Miliband is a "winner" who will be elected prime minister at the next general election despite persistent criticism from within Labour ranks, shadow justice secretary Sadiq Khan will insist today.

The shadow justice secretary will defend Miliband from his critics and claim that it is the Tories and the Lib Dems that will be holding a leadership contest next May - not the Labour Party.

The Labour leader has had a difficult start to the summer, with some shadow cabinet ministers briefing against him in the newspapers and veteran party figures publicly questioning his strategy. Miliband's head of policy, Jon Cruddas, was also recorded criticising the policy "dead hand" at the centre of the party.

Khan will use a speech at UNISON's political conference in Bristol to issue a strong riposte. His words are notionally directed at Conservative opponents, but are also intended to slap down internal shadow cabinet critics. Khan is a close ally of Miliband and ran his 2010 leadership campaign.

Labour is usually cautious about appearing overly confident that it will win the 2015 election. However Khan will make one of the boldest predictions from a senior party figure to date.

"Ed Miliband is a winner and he will walk into Downing Street in less than 10 months. It’s because he’s a winner that he’s getting flak in the media. He’s got them worried and their instinct is to play the man not the ball," he will say.

And he will say he expects the attacks on Miliband to "intensify as the Tories sense their time is up and Cameron desperately tries to cling to power" over the next ten months.

Khan will add: "There WILL be a Leadership election after the general election. But you’ll only get to vote if you are a Tory or a Lib Dem. When we unceremoniously boot them out of office after just one term, the Tories and Lib Dems will dump their failed leaders and look for new ones."

Last month The Guardian reported that some members of the shadow cabinet were clear that Miliband would have to quit as Labour leader if he failed to win the election. "Ed really cannot stay on if he loses – that really would not work," one frontbencher told the paper. "He has to go if we lose," said another.

Despite Miliband's attempt to move the debate onto the economy, Westminster remains largely fixated on his leadership. One shadow minister even told The Times: "What some of us fear is that we’re going to win, but Ed could be such a terrible leader we’ll be out for a generation after that." Khan's comments are likely to be interpreted as a demand that his colleagues fall into line and focus their attacks on the Conservatives.

In his speech Khan will also attack the coalition for "systematically demolishing the pillars of a fair and just society". He will accuse David Cameron and Nick Clegg of having "gone further than Margaret Thatcher could have dreamed in attacking our most cherished institutions - weakening the NHS, our education system, local government and the criminal justice system".

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