Jeremy Corbyn has failed to provide "consistent leadership" in tackling anti-Semitic abuse within the Labour ranks, a damning report by MPs has concluded.
The cross-party Home Affairs Select Committee questioned whether Mr Corbyn "fully appreciates" the nature of post-war anti-Semitism and also sharply criticised the inquiry into the issue by Labour peer Baroness Chakrabarti.
Labour was accused of "incompetence" over its handling of high-profile allegations of anti-Semitism including those involving former London mayor Ken Livingstone and Jackie Walker, who was recently removed as vice-chairwoman of the Corbyn-supporting Momentum group.
"The failure of the Labour Party to deal consistently and effectively with anti-Semitic incidents in recent years risks lending force to allegations that elements of the Labour movement are institutionally anti-Semitic," the MPs warned.
Responding, Mr Corbyn suggested the report was biased against Labour, described the criticism of Lady Chakrabarti as "unfair" and said the committee "violated natural justice" by refusing her request to appear before it.
The Labour leader said: "The report's political framing and disproportionate emphasis on Labour risks undermining the positive and welcome recommendations made in it.
"Although the committee heard evidence that 75% of anti-Semitic incidents come from far-right sources, and the report states there is no reliable evidence to suggest anti-Semitism is greater in Labour than other parties, much of the report focuses on the Labour Party.
"As the report rightly acknowledges, politicising anti-Semitism - or using it as a weapon in controversies between and within political parties - does the struggle against it a disservice."
The committee's strongly-worded report was agreed in full by the two Labour MPs on the panel - Chuka Umunna and David Winnick.
A third Labour member of the committee, Naz Shah, took no part in the inquiry after she was suspended from the party over anti-Semitic social media posts before later having the whip reinstated after apologising.
Mr Corbyn gave evidence to the committee but the MPs questioned his understanding of the issue.
"While the Labour Leader has a proud record of campaigning against many types of racism, based on the evidence we have received, we are not persuaded that he fully appreciates the distinct nature of post-Second World War anti-Semitism," the report said.
Jewish Labour MPs have been subject to "appalling" levels of abuse, including death threats from individuals claiming to be supporters of Mr Corbyn, the report said.
"Clearly, the Labour leader is not directly responsible for abuse committed in his name, but we believe that his lack of consistent leadership on this issue, and his reluctance to separate anti-Semitism from other forms of racism, has created what some have referred to as a 'safe space' for those with vile attitudes towards Jewish people.
"This situation has been further exacerbated by the Party's demonstrable incompetence at dealing with members accused of anti-Semitism, as illustrated by the saga involving the suspension, re-admittance and re-suspension of Jackie Walker.
"The ongoing membership of Ken Livingstone, following his outbursts about Hitler and Zionism, should also have been dealt with more effectively.
"The result is that the Labour Party, with its proud history of fighting racism and promoting equal rights, is seen by some as an unwelcoming place for Jewish members and activists."
The committee welcomed the inquiry set up by Mr Corbyn, but they expressed doubts about its independence after its chairwoman, former Liberty director Baroness Chakrabarti, joined Labour and accepted a peerage.
The MPs said the Chakrabarti report was "clearly lacking in many areas".
"The fact that the report describes occurrences of anti-Semitism merely as 'unhappy incidents' also suggests that it fails to appreciate the full gravity of the comments that prompted the inquiry in the first place," the MPs noted.
"These shortfalls, combined with Ms Chakrabarti's decision to join the Labour Party in April and accept a peerage as a nominee of the Leader of that Party, and her subsequent appointment as shadow attorney general, have thrown into question her claims (and those of Mr Corbyn) that her inquiry was truly independent."
The MPs said Lady Chakrabarti had not been "sufficiently open" about when she was offered the peerage and did not foresee that the timing of her elevation to the Lords alongside a report "absolving" Mr Corbyn of responsibility for anti-Semitism "would completely undermine her efforts to address the issue".
"It is equally concerning that Mr Corbyn did not consider the damaging impression likely to be created by this sequence of events," the MPs said.
Former London mayor Mr Livingstone was suspended from Labour in April after arguing that Hitler had supported Zionism in the early 1930s.
The MPs said his comments were "unwise, offensive and provocative" and they believed it was "likely" that he knew they would cause offence.
"In the words of Mr Corbyn, who described himself as his friend, we hope that Mr Livingstone will 'mend his ways' without delay," the report said.
The report also criticised Liberal Democrat leader Tim Farron over his handling of allegations within his own party, particularly involving former MP David Ward.
"We were disappointed by the manner in which their Leader, Tim Farron, referred to disciplinary processes rather than explicitly condemning anti-Semitic remarks made by members of his party, and we were surprised to learn that Cllr David Ward remains an elected representative of the Liberal Democrats, despite his repeated anti-Semitic comments," the report said.
The report noted that while the UK remains one of the least anti-Semitic countries in Europe, "it is alarming that recent surveys show that as many as one in 20 adults in the UK could be characterised as 'clearly anti-Semitic'.
The MPs also highlighted a disparity in police recording of anti-Semitic crime across and called on the National Police Chiefs' Council to investigate.
"There is a real risk that the UK is moving in the wrong direction on anti-Semitism, in contrast to many other countries in Western Europe," the MPs said.
"The fact that it seems to have entered political discourse is a particular concern."
Tim Loughton, the committee's Tory acting chairman, said: "History shows that anti-Semitism is a virus that is too easily spread, through subtly pernicious discourse, ignorance and collusion.
"We call on all leaders of political parties to lead by example to tackle the growing prevalence of this insidious form of hate, opposing racism and religious hate in all its forms and working harder to promote inclusion and understanding among party members and the wider public, as befits the UK's status as a multicultural, multi-ethnic, multi-religious society."