Andy Burnham's allies have reportedly launched a furious assault on Wes Streeting, accusing him of deliberately sabotaging the mayor's path to Downing Street by reigniting Labour's Brexit battles, and handing a gift to Nigel Farage in the process.
The bitter falling-out erupted after Mr Streeting, who resigned as health secretary last week, used the weekend to call for Britain to rejoin the European Union, describing Brexit as a "catastrophic mistake." He told supporters: "Britain's future lies with Europe, and one day back in the European Union."
Mr Burnham's camp is understood to have interpreted the move as a deliberate act of political sabotage, an effort to flood the Makerfield contest with Brexit noise in a seat the mayor cannot afford to lose, having staked his entire leadership bid on winning it.
One Burnham ally was reportedly blunt: "Wes's only hope at becoming the next leader is for Andy to lose the by-election. [Streeting's] comments … are counterproductive to Labour winning this by-election. It's very transparent."
A senior government source went further: "I despair. It's like a gift to Farage. What Wes did reeks of desperation and selfishness." An MP close to Mr Burnham described the move as a "roll of the dice" by Mr Streeting, saying "he can see the writing is on the wall," while a friend of the mayor said he was "clearly trying to create a dividing line."
The public feuding prompted a cabinet minister to remark that the battle between the two men was making Sir Keir Starmer look like an "island of stability and sanity" and to call on both to step back from the brink, The Times reported .
Culture Secretary Lisa Nandy, widely seen as a Burnham ally, publicly rebuked Mr Streeting, warning Labour against "reopening the Brexit wars" and likening the prospect to declaring "life was fine in 2015, we just need to go back there." Connor Naismith, Labour MP for Crewe and Nantwich, welcomed Mr Burnham "making clear that the priority for Britain must be domestic issues in the here and now, not restarting a debate about Europe."
A source close to Mr Streeting pushed back, arguing his position was hardly controversial given that Mr Burnham had also backed EU membership. "I thought they agreed on this," the source said. "The problem is that we're so worried that there might be people who disagree with us if we do something that we end up doing nothing. We're in a situation where the last parliament was the worst on record for living standards and this is the second [worst]. The only way out of this decline is if we address these big issues and tackle them head-on."
Behind the scenes, the Prime Minister is understood to be torn — pulled in different directions by advisers split on whether he should set out a departure timetable immediately or sit tight and see what the Makerfield vote delivers.
No 10's calculation is straightforward: a Burnham win makes Starmer's position untenable. But those loyal to the Prime Minister see a different path — one in which a stumble by Mr Burnham in Makerfield leaves Sir Keir strong enough to see off Mr Streeting in any subsequent contest.
The Times also revealed that Angela Rayner, the former deputy prime minister, was approached by No 10 about taking over from Mr Streeting as health secretary — but turned the offer down.
Farage has made his intentions clear, telling The Times voters would face a straight choice: Reform, which wanted to "stay outside of the EU [and] control immigration", and Labour, which he said wanted to "rejoin the EU and open the borders." He branded the mayor "open-borders Burnham."
Mr Burnham has attempted to limit the damage, arguing that while there is a "case" for rejoining the EU he will not "advocate" for it during the by-election campaign. However, his own words at last September's Labour Party conference are already being used against him. He told delegates: "Long term — I'm going to be honest, I'm going to say it — I want to rejoin it."
Those around him acknowledge the scale of the challenge. At the general election, more people voted Reform in Makerfield than in any other Labour-held seat. Josh Simons, the MP standing aside to make way for Mr Burnham, told the BBC that Labour faced an "existential crisis" if it lost the seat.
Despite the turbulence, Mr Burnham's campaign team remain confident in their strategy. A local source said simply: "We will put his face absolutely everywhere."
