Labour's anti-Semitism scandal erupted into full-scale civil war last night after two of Jeremy Corbyn’s most senior hard-Left allies exchanged insults over the issue.

A party chief close to MP Chris Williamson, who was suspended by Labour this week for saying it was ‘too apologetic’ over anti-Semitism, admitted threatening to ‘do in’ the founder of Momentum, Mr Corbyn’s Left-wing power base.

Leaked emails seen by the Daily Mail show that Momentum’s Jon Lansman claimed Pete Willsman, a member of Labour’s ruling National Executive Committee, threatened to ‘do him in’ in a feud over anti-Semitism.

Leaked emails seen by the Daily Mail show that Momentum's Jon Lansman (above) claimed Pete Willsman, a member of Labour's ruling National Executive Committee, theatened to 'do him in' in a feud over anti-Semitism

In the messages Mr Lansman, who is Jewish, brands hard-Left rival Mr Willsman a ‘hateful, embarrassing dictator and crank’.

He says Mr Willsman ‘waited two hours outside a room in which I was engaging in a telephone conference to threaten me when I emerged, “I am going to do you in” ’. He says they were Mr Willsman’s ‘precise words’.

Mr Willsman avoided being thrown off the NEC in September after he was recorded saying that Jewish ‘Trump fanatics’ were ‘making up’ anti-Semitism allegations in Labour, comments condemned as ‘sickening’ by moderate Labour MPs.

Mr Willsman was furious when Mr Lansman’s Momentum withdrew its support for him in NEC elections in September.

He survived after Mr Williamson came to his rescue, urged Labour members to vote to keep Mr Willsman on the NEC and brushed aside the furore over his ‘fanatics’ outburst.

He says Mr Willsman (above) ‘waited two hours outside a room in which I was engaging in a telephone conference to threaten me when I emerged, “I am going to do you in” ’. He says they were Mr Willsman’s ‘precise words’.

Mr Willsman retained his NEC seat and was ordered by Labour chiefs to apologise and go on anti-Semitism training.

But in January he called on his ‘empty-headed (Labour) critics’ to produce evidence to back up their ‘ridiculous assertion of widespread anti-Semitism in Labour’.

In the emails, sent two weeks ago, Mr Lansman says: ‘Comrade Willsman is consumed with hatred of me.

He has become an embarrassment to the Left and a serious risk to the reputation of Jeremy Corbyn and the Labour Party. His NEC contributions are cranky.’

He calls Mr Willsman a ‘stupid liar, belligerent and unpleasant – and is losing it’.

An ally of Mr Willsman hits back at Mr Lansman in the round robin emails, accusing Momentum of trying to ‘kill’ Mr Willsman in a ‘semi-public bitch fight’.

In stark contrast to the way Mr Williamson and Mr Willsman deny Labour anti-Semitism, Mr Lansman has won praise for stressing the party must root it out.

In the emails, sent two weeks ago, Mr Lansman says: ‘Comrade Willsman is consumed with hatred of me. He has become an embarrassment to the Left and a serious risk to the reputation of Jeremy Corbyn and the Labour Party. His NEC contributions are cranky'

He told the BBC last week that Labour has a bigger problem of members with ‘hardcore anti-Semitic’ views than previously acknowledged.

He spoke of his ‘enormous regret, sadness and some shame’ that MPs such as Luciana Berger, who is Jewish, had left the party.

Footage emerged this week of Mr Williamson, the MP for Derby North and a long-time Corbyn ally, telling a Momentum rally in Sheffield that the party had been too ‘apologetic’ over anti-Semitism.

The MP issued an apology but was suspended from the party after a furious internal backlash.

Mr Willsman last night confirmed he said he would ‘do in’ Mr Lansman, but told the Mail: ‘It is daft to suggest I meant I was going to do him in physically. I meant it purely in the political sense.’

He said he had offered to bury the hatchet in return for an apology, but Mr Lansman had refused. ‘He just laughed and walked away so I responded rather irritably.’

The Labour Party and Mr Lansman declined to comment.