The Socialist Workers Party was engulfed in crisis tonight over allegations that it set up a “socialist sharia court” to investigate rape allegations against a senior member instead of reporting them to the police.

The scandal, which has opened up deep splits within Britain’s largest far-left party, emerged this week when disaffected members leaked minutes of a controversial disciplinary meeting which exonerated the official accused of rape and sexual assault.

The furore has led to the expulsion of key members and multiple resignations.

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Today Tom Walker, a journalist at the party’s paper, Socialist Worker, became the most prominent member to quit the party in disgust.

In a devastating critique published on the rival Communist Party of Great Britain’s website, Walker excoriated the SWP’s handling of the rape accusations, alleging that the hearing as a “kangaroo court” and “amateur justice that was doomed from the start”.

The minutes of the disciplinary meeting, which was held during the party’s December conference, detail how SWP leaders were determined to keep the matter away from the police and official authorities – with one member stating that the party had “no faith in the bourgeois court system to deliver justice”.

The row is just the latest sexism scandal to tarnish the reputation of Britain’s radical left which tends to portray itself as a fierce advocate for women’s rights. In September, the Respect Party’s former leader, Salma Yaqoob, quit in protest over comments made by its founder, George Galloway, that the accusations against WikiLeaks founder Julian Assange simply constituted “bad sexual etiquette” and not rape.

The highly detailed minutes, which run to 27 pages, were first published on Socialist Unity, a left wing blog run by Andy Newman, a Swindon-based Labour Party member. He told The Independent that SWP members contacted him anonymously because they were furious about the way the party had handled the rape allegations.

“I believe that the SWP think they’re outside the law,” he said. “It’s quite clear reading their account of what’s going on that they sort of see themselves as an alternative group in society that is not part of mainstream society. They think someone couldn’t or shouldn’t go to the police because it would damage the party.”

Mr Newman likened the SWP’s disciplinary hearing to an extrajudicial “sharia” system or the much criticised investigations by the Roman Catholic church into clerical abuse that bypassed reporting allegations to the authorities.

The minutes detail how the party’s disciplinary committee met to discuss allegations that had been levelled against “Comrade Delta” – a senior member who sat on the party’s central committee.

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The allegations came from an unnamed female party member who claimed she was assaulted over a six-month period between 2008 and 2009 but did not want to go to the police. The disciplinary committee exonerated Comrade Delta with six of the seven panel members backing his version of events. However, in an indication of the huge concerns over how the case was handled, the panel’s findings were only narrowly accepted by 231 votes to 209 votes when they were put to party members.

The minutes show how party activists attacked panel members for admitting that they knew Comrade Delta personally. One panel member conceded: [We] all knew Comrade Delta. We knew his important role in the party and on the central committee and none of us knew W or knew her well.”

In his resignation letter, journalist Tim Walker wrote: “Though I believe they took the case deeply seriously, this was not a jury of his peers, but a jury of his mates.”

According to the minutes, friends of the woman – who was not allowed to attend the meeting – stood up to say she felt betrayed by the party. One supporter said: “She thought that if she put in a complaint to the party it would be dealt with in line with the party’s politics and our proud tradition on women’s liberation. Sadly her experiences were quite the opposite.”

The Independent contacted the SWP head office for comment on the allegations but received no reply.

The party’s national secretary, Charlie Kimber, did not dispute the veracity of the minutes in a letter to Socialist Unity demanding they be taken down from the internet.

“I do not believe you are motivated by any considerations apart from a desire to damage the individuals involved and the SWP and to achieve tawdry publicity,” Mr Kimber wrote.

Mr Newman denied the allegations, saying he deliberately redacted the names of those who spoke to protect their identities. What was said in the disciplinary hearing was of public importance and justified publication.

The SWP, formed in 1977 out of the International Socialists, describes itself as a “revolutionary socialist party” in the tradition of Leon Trotsky.