UNITE general secretary Len McCluskey condemned Blair-era traitors and the Tory-supporting mass media yesterday as he pledged allegiance to Ed Miliband in front of hundreds of activists in Birmingham.

The leader of Britain’s biggest union hit out at a relentless smear campaign targeting the Labour leader including front-page attacks in the Times and Telegraph.

Among those lining up to shoot down Mr Miliband are a gaggle of former leading party figures who served in multi millionaire Tony Blair’s government.

Mr McCluskey said the battle lines had now been drawn for “a fight for the future of our society, for the poor and vulnerable,” urging the Labour leader to stick to his guns and face down his attackers.

“The electorate is today poised between fear and hope,” said the Unite general secretary.

The Tories planned “tear to bits every advance working people have secured, every protection we have built up, over the years.”

But following the election of left-wing populist party Syriza in Greece, “hope is blossoming,” said Mr McCluskey.

“Labour needs to bottle some of the Syriza spirit and take that anti-austerity agenda to the people here.

“What it doesn’t need is the Blairite retreads — the people who sucked the life out of the last Labour government — attacking every progressive impulse, like the mansion tax and saving our NHS.

“So I say to Peter Mandelson, Alan Milburn and John Hutton — stick to counting your money and stop stabbing Labour in the back.”

Unite agreed last week to release £1.5 million towards Labour’s election campaign.

But the party’s budget will be dwarfed by the Conservatives, who have received millions from City donors.

Mr McCluskey declared that the union had stumped up the cash because it had a “duty to democracy.”

He said: “Let the Tories get their millions from hedge funds and from shadowy dinner clubs of big businessmen.

“Our money is clean, transparent to the public, democratically sanctioned and honestly accounted for.

“It’s the pennies of our members each week, not the ill-gotten gains of the ruling elite.”

He urged his 1,200-strong audience to “get behind your union and its political strategy, and get behind a Labour victory in May.”