LABOUR leftwingers are switching their second-preference votes from Andy Burnham in protest at his “rightwards trajectory,” the Morning Star can reveal.

Leadership hopeful Mr Burnham provoked fury yesterday when he used an newspaper interview to savage the mansion tax as “spiteful.”

His outburst came as the heads of two non-Labour-affiliated trade unions urged activists to sign up as registered supporters of the party to vote for left challenger Jeremy Corbyn.

Mr Burnham told the Mail on Sunday: “My ambition is to enable all people who want a ladder into home ownership to have one. It’s a strong instinct in most British people.

“A sense has built up that we aren’t in favour of people getting on. That is toxic.”

The party leader is elected by the preference-based alternative vote system.

It is understood Mr Corbyn’s supporters are increasingly likely to give their second preferences to shadow foreign secretary Yvette Cooper.

A number of leftwingers said Mr Burnham’s comments had lost him their support.

Susan Press, a councillor in Calderdale, west Yorkshire and veteran Labour Representation Committee activist, told the Star that Mr Burnham had been “all over the place.”

“Most of us were still inclined to give [him] a second preference but that’s increasingly in doubt,” she said.

“One minute it’s the best manifesto he’s ever stood on, the next he’s criticising policies like the mansion tax.

“It’s a trajectory going to the right and it’s a serious error. He could lose a lot of support.”

A party lay officer in east London who, like Ms Press, was planning to second-preference Mr Burnham said: “He’s just lost thousands of Corbyn second preferences.

“I’ve reconsidered and I think I’ll give Cooper the transfer. I know others are thinking this way too.”

Another Corbyn supporter, London Young Labour executive member Rachael Ward, said: “I never understood why people on the left were supporting Andy. Yvette’s defence of Labour’s spending record and her policies on expanding childcare should make her far more appealing to the left.”

At the People’s Assembly rally in London on Saturday, PCS general secretary Mark Serwotka urged the crowd to pay the £3 registration fee to take part in the vote.

And FBU general secretary Matt Wrack said: “It should be a no-brainer … that the trade unions back Jeremy Corbyn in the Labour leadership election.”