A Labour campaign group headed by John McDonnell has attacked the party's ruling body for refusing to allow a controversial former MP to stand at the general election.
The Labour Representation Committee (LRC), of which the shadow chancellor is president, urged members to "express their anger in every way they can" after the National Executive Committee refused to adopt Chris Williamson as a candidate.
The LRC's position is likely to raise further questions about Mr McDonnell's personal stance on the issue, after he refused to say in a radio interview last week whether he thought Mr Williamson should be allowed to stand.
Mr Williamson, a close ally of Jeremy Corbyn, was suspended in February in a row over-anti-Semitism, when the Labour leader's office said he would be investigated over a "pattern of behaviour”. His suspension came after the Yorkshire Post revealed that he had told activists that Labour had been "too apologetic" over anti-Semitism and was being "demonised as a racist, bigoted party".
In a statement published on its website, the LRC said Mr Williamson had been the subject of "false allegations" of anti-Semitism. It said: "The fact is that he has been a doughty supporter of Jeremy’s Corbyn’s leadership. That is his real ‘crime’."
The Telegraph has previously revealed how the LRC, with which Mr McDonnell has been associated since its formation in 2014, has campaigned in support of Labour figures accused of anti-Semitism and verbal abuse of an MP. But Mr McDonnell has resisted pressure to resign from his role. In February he spoke at the group's annual conference, when he was reconfirmed as the group's president.
Mr Williamson served as MP for Derby North from 2010 to 2015 and then again from 2017, having lost the seat in the 2015 election.
Earlier this year he was also criticised for booking a room in Parliament for a screening of a film about anti-Semitism and the activist Jackie Walker, who was suspended by Labour in 2016 over remarks in which she described Jews as "chief financiers of the sugar and slave trade". Ms Walker says she is of Jewish descent and describes herself as an anti-racism campaigner.
The LRC described the NEC's decision to bar Mr Williamson from standing as a Labour candidate on Dec 12 as "cowardly", adding: "The bizarre and inconsistent stance of the NEC amounts to Labour shooting itself in the foot in the middle of the campaign.".
It added: "This is a bad day for Labour Party democracy and for the future of our Party. Members should express their anger in every way they can. "
After Mr Williamson's comments were reported in February, he insisted that he had not intended to "minimise the cancerous and pernicious nature of anti-Semitism."
But Dame Margaret Hodge, a Jewish Labour MP, said at the time of his suspension: "He has form. He has done this before, he has apologised before and then he has done the same thing again.
"In the current climate not to show strong, immediate, determined action to stand out anti-Semitism was a mistake. The fact it has finally happened is a relief."
Asked for his view on whether Mr Williamson should be suspended, Mr McDonnell told LBC ahead of the decision: "I don't want to prejudice the hearings that are taking place at the moment."
When Iain Dale, the presenter, said that Jewish people "think that is yet another example of the Labour party equivocating over somebody who has clearly made remarks that people consider anti-Semitic", Mr McDonnell said: "Some consider anti-Semitic. That is what Chris is challenging at the moment."
Following the NEC's decision Mr Williamson again denied anti-Semitism. He claimed that party officials had "capitulated to the Jewish Labour Movement" - one of Labour's oldest affiliate groups - in remarks that prompted renewed outrage among Labour backbenchers.
The Labour Party has repeatedly insisted that Mr McDonnell "has no day to day involvement in the operation of the LRC and is not responsible for its website."
A spokesman for Mr McDonnell said: "John has no day to day involvement in the operation of the LRC and is not responsible for comments it makes and political positions it takes."