Jeremy Corbyn should no longer get "the benefit of doubt" over whether his personal politics are contributing to the rise of antisemitism within Labour, a leading expert on left-wing Jew-hate has said.

Speaking at the packed Westminster launch of his updated book The Left's Antisemtism Problem, Dr Dave Rich said: "Three years ago when people wrote articles about antisemitism in the Labour Party they usually included the caveat saying nobody is accusing Jeremy Corbyn of being antisemitic himself. 

"I don't think he gets the benefit of that doubt anymore."

Dr Rich, who is also head of policy at the Community Security Trust, spoke to an audience that included Labour MPs Ruth Smeeth, Joan Ryan, Luciana Berger, Dame Margaret Hodge, John Mann and Alex Sobel.

He said that Mr Corbyn was part of a far-left tradition, born in the 1960s, that was obsessed with taking an "anti-imperialist" stance.

"Three years ago things were bad," he said. "When Corbyn became leader there were questions raised about people he'd shared platforms with, about organisations he'd endorsed, questions he didn't answer. 

"But it didn't need to get as bad as it is now."

Dr Rich said that, while Mr Corbyn "understood anti-racism", he failed to recognise how remarks - such as his 2013 comments that British "Zionists" fail to grasp "English irony" - would be deemed racist were made about any other minority except Jews.

Dr Rich listed Mr Corbyn's controversial actions and statements involving Jewish concerns - including his reaction to an antisemitic mural in Tower Hamlets and his attendance at the Black September wreath-laying ceremony in Tunisia in 2014.

"He's made too many mistakes in this area for them all to be mistakes,"  Dr Rich said. "It's a pattern of behaviour easily explained by accepting this is what he believes."

Dr Rich said Mr Corbyn was a "product of antisemitic culture on the left". 

He was also scathing of the Labour leader's stance on Israel, which, he said, Mr Corbyn's section of the left regarded as "a relic of European colonialism that should never have been created".

Attacking the left's obsession with anti-Israel ideology, Dr Rich said: "Instead of spending the summer hammering the government over Brexit and austerity and housing and every other issue that needs to be dealt with, they spent the summer arguing with a community of 300,000 over whether half a clause in a definition most people hadn't read should be adopted by their internal disputes structure."

But in a more positive light, Dr Rich said the Jewish community has "strong institutions and strong traditions" as well as the "tools, resources and confidence" to face up to the challenge of rising antisemitism.

He said:"I think the Jewish community here has strong institutions and strong traditions and I think we have the tools and resources and confidence to deal with this challenge."

He said while antisemitism had found itself into the mainstream political arena in Britain "broad attitudes" across the country meant that "In many respects" the issue was not as bad here as it is in other countries.

"There is a way out of this and the Jewish community is strong enough to get through it," he said.

"It is going to require a change from within. It is going to require people and networks within the Labour Party to actually stand up and demand this change from the leadership."

Labour MP Ian Austin also spoke, saying a number of his constituents had expressed anger about Mr Corbyn's failure to tackle his party's antisemitism crisis.

"The Jewish community should not underestimate the support they have from ordinary decent people," he said. "Millions will not vote for a party that has been mired in a scandal like this and will not root it out."

He responded to questions from the audience - who also included Holocaust Educational Trust chief executive Karen Pollock, Countdown presenter Rachel Riley and former Labour NEC member Jasmin Beckett.

Mr Austin said Labour was now led by people "compeletely outside" the party's "mainstream".

He called for "mainstream social democrats" to "stand up" to take back control of the party.