The co-chair of a leading student Labour group has quit amid accusations that colleagues “have some kind of problem with Jews”.

Alex Chalmers said he was leaving the "poisonous" Oxford University Labour Club (OULC) after it endorsed Israel Apartheid Week, due to take place next week.

Mr Chalmers claimed fellow students had expressed “solidarity” with Hamas and had claimed accusations of antisemitism were “just the Zionists crying wolf”.

His remaining co-chair said the club took accusations of antisemitism "very seriously".

In a lengthy Facebook post published following his resignation on Monday evening, Mr Chalmers wrote that he had invested "an extraordinary amount of time, energy, and emotion" in the club.

But it had become "increasingly riven by factional splits, and despite its avowed commitment to liberation, the attitudes of certain members of the club towards certain disadvantaged groups was becoming poisonous".

Students had used the term "Zio" with "casual abandon" he wrote.

They had also expressed "their 'solidarity' with Hamas and explicitly defending their tactics of indiscriminately murdering civilians".

Mr Chalmers claimed one colleague had claimed that "most accusations of antisemitism are just the Zionists crying wolf".

"A large proportion of both OULC and the student left in Oxford more generally have some kind of problem with Jews," he added.

"The decision of the club to endorse a movement with a history of targetting and harassing Jewish students and inviting antisemitic speakers to campuses, despite the concerns of Jewish students, illustrates how uneven and insincere much of the active membership is when it comes to liberation.

"I am now in a position where I can no longer in good conscience defend club policy, but I do not regret my time in OULC. I'm proud of the work I did."

Noni Csogor, Mr Chalmers's co-chair, said she respected his decision to quit.

On the group's 18-16 vote in favour of backing the apartheid week, she wrote: "We did not vote on a blanket position on the Israel-Palestine conflict; we voted to support Oxford’s Israeli Apartheid Week.

"At Oxford, IAW has hosted a wide variety of Israeli, Palestinian, and South African speakers, such as Denis Goldberg, who fought against apartheid in South Africa, and Oxford professors like Avi Shlaim, Karma Nabulsi, Sudhir Hazareesingh, and David Priestland.

"As the motion notes, OULC and the Labour Party have always been against racism and oppression in all its forms; this must include the policies of the current Israeli government."

Ms Csogor added: "Alex is right to highlight growing antisemitic violence in the UK as a major issue; it’s also horrifying that Jewish students feel unsafe on campuses.

"It’s unsurprising, given incidents like that at KCL Israel Society a few weeks ago, and I’m sure OULC members would join me in condemning the silencing of Jewish students, who often have uniquely nuanced perspectives on the Israeli state.

"Jewish students spoke on both sides of the debate this evening, but we take allegations of antisemitism in the club very seriously and I will be discussing, with my executive committee, how to deal with the kinds of statements Alex mentions, and what concrete steps we can take in future to preserve a club that’s been a safe haven for Jewish students in the past.

"I understand Alex’s position, but am looking forward both to running the events we’ve organised for the rest of the term, and to contributing to an ongoing discussion about the complex intersection of justice for Palestine and the safety of Jewish students."

Russell Langer, Union of Jewish Students campaigns director, said: "The reports of antisemitism coming out of the Oxford University Labour Club (OULC) are extremely concerning.

"These reports, along with the decision of OULC to endorse Israeli Apartheid Week show that OULC are against the interests of Jewish students."

Mr Langer said Mr Chalmers' decision to resign was "brave".

"Considering the number of senior politicians who have passed through OULC I hope that this matter is investigated urgently by the Labour Party with appropriate action taken," Mr Langer added.

He said UJS had an "extremely positive relationship" with Labour student groups nationally.

Oxford University Jewish Society said it was “saddened” by the reports and backed Mr Chalmers’s decision to resign.

In a statement the JSoc said: “We are, however, unsurprised by this news. It is not the first time that Oxford JSoc has had to deal with antisemitic incidents within the student left and it will not be the last.

“It is a significant and worrying issue and one that on many occasions Jewish students have felt that they are fighting alone. We are grateful that Alex Chalmers has made the statement that he did and has brought the issue of antisemitism to the fore in a way that Jewish students have so far been denied.

“Oxford JSoc strongly rejects any accusation that Jewish students are inventing claims of antisemitism to discredit Palestinian solidarity politics.

“This is a repeated trope that has been used to silence Jewish students and it will carry weight no longer. When antisemitism intersects with Palestinian solidarity politics, it is not the job of Jewish students to be quiet, but the job of Palestinian solidarity activists to rid their movement of anti-Jewish prejudice.”

The JSoc statement said that Jewish students who had raised issues of antisemitism at the OULC meeting had been “laughed at and mocked”.

Labour Students, the umbrella group for the party’s student movements, said it was “deeply troubled” by the episode.

“We unequivocally condemn any form of antisemitism. We are taking these allegations very seriously and will do whatever is necessary to ensure every Labour club is a safe space for Jewish students.

“We are proud of the long history we have of working with the Union of Jewish Students and the National Union of Students to protect Jewish students on campus and this will always be a top priority for Labour Students.”

The Jewish Labour Movement said the episode had "crossed the red line between legitimate discourse and incitement against Jewish students".

Oxford University said in a statement: "The University does not tolerate any form of harassment or victimisation, including on the grounds of religion and belief, and expects all members of the university community, its visitors and contractors to treat each other with respect, courtesy and consideration."