Burnham is facing backlash over his shared platform with the Greens

Labor MPs have turned on Andy Burnham, who agreed to share a platform with the Greens just weeks after the local election.

The Mayor of Greater Manchester will attend a conference for the ‘progressive majority’ with former Green Party leader Caroline Lucas.

But Labor MPs reacted angrily to him siding with his rivals on the heels of a bitter local election battle.

The Greens are expected to storm traditional Labor territory and win a number of council seats from Sir Keir Starmer’s party in local elections.

They are expected to capture Labor strongholds in east London such as Hackney, Lewisham, Lambeth and Waltham Forest.

They could even make gains in Sir Keir Starmer’s home town of Camden, as well as Greenwich, Southwark and other Labor heartlands.

While Zack Polanski’s party has suffered a slight decline in the polls after some Green candidates made anti-Semitic comments, it still poses a major threat.

Labor MPs said they were unimpressed by Mr Burnham’s decision and said it would allow people to vote, with the Greens arguing they were aligned with Labour.

A Labor MP said of the event: ‘I was not impressed. There will also be many former council leaders and councilors who will be upset about this.

‘This gives people the green light to vote for the Greens by implying that a more Left-wing Labor Party is closer to the Greens than the KS.’ [Keir Starmer’s] ‘Workforce.’

Another Labor MP said: ‘The Greens are getting the airtime Burnham desires.

‘He did nothing to combat antisemitism when he was an MP, he acted like a leftist when he was a Blairite minister.

‘He now continues the same unprincipled approach while embracing the Greens.’

Following Labour’s expected defeat in local elections, Sir Keir is likely to face pressure from MPs who want to replace him.

Mr Burnham is seen as one of the most likely candidates despite the Prime Minister blocking him from running in by-elections earlier this year.

But his decision to appear alongside the rival Green party will upset Labor MPs who are fighting to keep their councils.

Left-wing group Compass and the Progressive Economic Forum event will be held in London on Saturday, May 30, with the aim of ‘mobilising the progressive majority’.

‘Speakers from some of the largest progressive parties and organizations will come together and figure out: how [do] “We are transforming the country’s progressive majority into power,” he says.

Speakers will include left-wing MPs and figures from the Labor Party, Greens and Liberal Democrats.

Clive Lewis, who is on the left of the Labor Party and has previously offered to stand down to make room for Mr Burnham, will also speak.

Communities minister Miatta Fahnbulleh will also speak at the event, as will several Liberal Democrats, including Vince Cable.

The event says it will bring together ‘progressives of all parties (and none)’ for a day filled with ‘debate, disagreement and negotiation’.

Compass founder Neal Lawson has long campaigned for a progressive cross-party alliance but is also a key supporter of Mr Burnham.

A source close to Mr Burnham said: ‘Andy does not share a platform and to suggest he supports other parties is nonsense; he is developing progressive ideas to help Labor.

‘Don’t people want anyone to share their ideas or debate progressive policies?’