Labour quietly reinstated at least six councillors who posted anti-Semitic messages online, analysis shows, as a party insider told The Telegraph the complaints process is being manipulated by political factions.

Evidence seen by The Telegraph shows senior party members were investigated over posts made on social media, including messages about blood libel, Zionism, linking Israel to Isis and the Holocaust and other anti-Semitic tropes.

All six were reinstated quietly by the party, raising questions about whether Labour's process for rooting out racism is effective. It is unclear whether any disciplinary action was taken before they were cleared.

It came as Labour MPs also expressed “serious concerns” about the track record of the party’s new General Secretary.

Jennie Formby, the woman tasked with purging the party of anti-Semitism and a close ally of Jeremy Corbyn, is alleged to have called for a ban on the security firm G4S tendering for work with Labour because of “its work in Israel”.

Jennie Formby: Labour's new General Secretary credit: Stefan Rousseau/PA Wire

She is also alleged to have challenged the appointment of a Labour peer to conduct an unrelated anti-Semitism inquiry because she once visited Israel.

John McDonnell admitted Labour had not done enough to tackle the problem and said mechanisms to deal with anti-Semitism should have been introduced "ages ago".

Sources have told The Telegraph that Christine Shawcroft, who stepped down as the chair of the disputes panel but not as a member of the committee, attempted to get a number of other allies reinstated after they posted anti-Semitic messages.

She was blocked from doing so by other members of the disputes committee who raised concerns about her demand they be allowed back in if they undertook "training".

Margaret Beckett is said to have been one of the MPs who opposed the move earlier this year.

Some 39 MPs and peers have signed an open letter calling for Ms Shawcroft to be suspended from the National Executive Committee (NEC).

Lead signatory of the letter, MP for Mitcham and Morden Siobhain McDonagh, told the BBC the group felt "very strongly" about the issue.

It came as a former member of the NEC said Ms Shawcroft's behaviour was "not unusual" and that she had a pattern of supporting people without questioning their behaviour fully.

Christine Shawcroft credit: LNP

One of the six councillors, Salim Mulla, is still an active Labour politician and was former mayor of Blackburn.

He was suspended in May 2016 but reinstated in February 2017 despite posting a number of anti-Semitic messages on Facebook. One accused Israel of being behind Isis attacks in Europe and another was the same post which Labour MP Naz Shah was suspended over, and which she later described as anti-Semitic.

Asked about the decision to allow him back into Labour, Mr Mull​a said at the time: "My social media posts were solely concerns about the treatment of Palestinians by the Israeli government and not about the Jewish people as a whole.”

Ilyas Aziz was also suspended in May 2016 and later allowed back into the party in December the same year. He is a siting Labour councillor in Nottingham and posted a number of anti-Semitic pictures and comments, including references to Zionism and the Rothschilds.

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Another of the six, Shah Hussain, was suspended after comparing Israel to Nazi Germany on social media but was reinstated in 2016. He doubled down on his comments at the time, saying they were “appropriate” and he was the victim of a “witch hunt”.

Andrew Slack and Luke Cresswell were both suspended in 2016 and later allowed back into the party - both are​ councillors for the party.

Mr Slack said he shared material online by accident.

The sixth was Miqdad Al-Nuaimi, a Labour councillor in Newport. He was suspended in May 2016 but allowed back into Labour just two months later.

The decisions have raised serious questions about the integrity of Labour's complaints process after a party insider told The Telegraph the disputes panel, which rules on cases of anti-Semitism and other wrongdoing, is being railroaded by political factions.

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The insider said some members of the panel, which are drawn from the party's National Executive Committee, will "defend any form of abuse if the person involved is perceived to be on their side of the party".

They added: "Dispute hearings have gone from being straightforward sessions to decide whether people need to be referred, to members arguing cases shouldn't be processed based on pure politics".

The insider said there was "shock" at a recent meeting where misogynistic, anti-Semitic and threatening behaviour was all being defended because of political alliances.

In a number of cases members of the committee came to meetings prepared with emails sent by supporters as proof that the accused could not be guilty because of the overwhelming support in their favour.

"It is all about political pressure", the said, adding that the whole process has become so toxic that it can no longer be trusted to get decisions right. "Every meeting has become a battle", they said.

MPs 'concerned’ over record of figure tasked with purging Labour anti-Semitism

Jennie Formby, a supporter of Christine Shawcroft, is also facing questions after she was alleged to have challenged the decision to appoint Baroness Royall to lead an investigation of anti-Jewish conduct by members of Oxford University Labour Club.

According to sources, Ms Formby questioned Baroness Royall’s links to Labour Friends of Israel and objected to her appointment in 2016 on the grounds that she had been to Israel.

A spokesman for Ms Formby said she “strongly refuted” the allegation, adding that Ms Formby had simply been arguing for Baroness Royall to be given the “right level of support”.

Ms Formby, an ex-lover of Unite leader Len McCluskey and mother to his child, is also alleged to have called for the security firm G4S to be barred from tendering for a security contract with the Labour Party due to “its work in Israel”.

She says she raised concerns about G4S for different reasons.

Speaking to The Telegraph on Thursday night, several Labour MPs said they had “serious concerns” about Ms Formby’s commitment.

They included John Mann, MP for Bassetlaw, who said: “Her actions in the next week will decide things one way or another. She has the opportunity to kick Christine Shawcroft off the national executive, to expel the anti-Semites, to get a proper system in place. She’ll be judged on her actions.”

Mr Corbyn tried to defuse the row by writing to Labour members insisting that anti-Semitism has “no place whatsoever in our Party”.