JEREMY Corbyn has faced an "explosive" meeting of Labour MPs and peers amid a heated row over claims of a hard Left takeover plot.

The party leader was heckled by MPs as he addressed the Parliamentary Labour Party[PLP] with some said to be angry at the suggestion that they were focused on infighting rather than campaigning.

The row erupted as a poll gave Theresa May’s Conservatives a 19-point poll lead over Labour despite last week’s humiliating Budget U-turn by the UK Government on its planned National Insurance Contributions rise for the self-employed.

Tom Watson, the deputy leader, said it was now clear the threat of a hard Left takeover was real after a recording emerged of Jon Lansman, the founder of Momentum, the grassroots activists group which helped propel Mr Corbyn to the leadership, discussing the prospects of gaining the support of Unite.

Mr Lansman was said to have told supporters he expected the union, together with the Communication Workers Union, to affiliate to Momentum if, as expected, Len McCluskey won his battle for re-election as General Secretary of Unite, Labour’s largest donor.

However, John McDonnell, the Shadow Chancellor and a close ally of Mr Corbyn, claimed Mr Watson's attack was an attempt to influence the Unite leadership contest, a claim backed up Gail Cartmail, the union's acting General Secretary.

Mr McDonnell said: "What he is trying to do is influence the election of the General Secretary of Unite and he has dragged the Labour Party into this, completely unnecessarily."

Earlier, Christine Shawcroft, Momentum’s director and who is a member of Labour's national executive committee, insisted: "This is about democratising the Labour Party, which will strengthen the Labour Party." She branded Mr Watson as "rather right wing" and claimed he wanted to go back to "command and control on a Blairite model".

After a stormy meeting of the Shadow Cabinet Mr Corbyn and Mr Watson issued a joint statement, emphasising the need to strengthen party unity. They said the meeting had been “robust” and constructive”.

Certain Shadow Cabinet members were said to have hit out forcefully at Mr Watson’s suggestion that the party's future was now at risk by the hard Left plotting a “secret deal” between Momentum and Unite.

One source said: "Jeremy was supported pretty much unanimously in Shadow Cabinet in slapping down Watson for what has been seen as a reckless intervention designed to influence Unite's general secretary election."

But later at the PLP meeting in the Commons MPs hit out at Mr Corbyn. One described the atmosphere as “explosive”.

Wes Streeting, a London MP, said: "What more evidence do they need about Momentum? Every member of the Shadow Cabinet who failed to speak out should search their consciences as they drive the Labour party off a cliff."

His Midlands colleague Ian Austin told Mr Corbyn to "look in a mirror," saying: "Having a mandate is one thing, actually being able to do the job is another."

Kezia Dugdale, the Scottish Labour leader, who addressed the PLP, derided the in-fighting, noting: “Never forget the best way to represent and deliver for working people will always be from the Government benches."

Earlier at a Shadow Cabinet “away day” at Unison's head office in central London, Mr Watson was allegedly rounded on by Mr McDonnell, Emily Thornberry, the Shadow Foreign Secretary, and Diane Abbott, the Shadow Home Secretary; all close allies of the leader.

One insider said: "The people who you would expect laid into Tom,” adding: "It was a brief and stormy discussion."

But Baroness Chakrabarti, a key member of Mr Corbyn's inner circle, was said to have been "influential" in reaching an agreement on the joint statement put out by the leader and his deputy.

Following the PLP, a source close to Mr Corbyn claimed most Labour MPs and peers agreed that groups within the party were free to try to influence it as long as it was within the rules.

"That's common ground to everybody, to both Tom and Jeremy, to the whole Shadow Cabinet and I'm sure to the large majority of the PLP," he added.