Members, activists and at least one MP of Britain's main opposition Labour Party described as "anti-Semitic" a member who challenged their pro-Israel ideas, despite some uncertainty over whether the member's comments were actually racist, an investigation by Al Jazeera has found.

The charges, made at September's Labour Party conference, led to the member being suspended pending a full investigation.

In total, the Labour Friends of Israel (LFI) said it had seen three cases of anti-Semitism during the first day of September's Labour Party conference, with the group of Israel supporters later debating the validity of two of them.

The complaints came in the wake of the Chakrabarti Inquiry, an investigation during summer 2016 into anti-Semitism within the Labour ranks. That report had concluded racism, including anti-Semitism, was not endemic within Labour.

Al Jazeera placed an undercover reporter within an influential group of politicians, activists and Israeli embassy officials working to drum up support for Israel, as part of a six-month investigation, The Lobby.

Ambassador: Anti-Semitic trend in left

The reporter, alias Robin, exposed the pivotal role of Shai Masot, who described himself as a senior political officer at the Israeli embassy.

Masot took Robin to the annual Labour Party conference in Liverpool, where they attended a briefing by the Israeli embassy.

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"Some of the people here are more Palestinian than the Palestinians," Mark Regev, Israel's ambassador to the UK, warned his supporters.

"The fashion is if you are on the left today you are probably very hostile to Israel, if not anti-Semitic."

Later, Robin covertly filmed a discussion at the Labour Friends of Israel (LFI) stand that saw a Labour activist investigated for racism following a discussion about a two-state solution between Israel and the Palestinians.

Heated discussion

A pro-Palestine activist, Jean Fitzpatrick, asked Joan Ryan, Labour MP and chair of LFI, whether the group was "very anti the settlements", referring to the illegal occupation of Palestinian land.

"We make our view clear and we meet with people at all levels in Israeli politics and diplomatic circles," Ryan replied, apparently avoiding answering the question directly.

"We believe in a two-state solution and the coexistence and self-determination for both people and that's really important."

Fitzpatrick then enquired about the group's funding and suggested it enjoyed a good reputation.

"You've got a lot of money, you've got a lot of prestige in the world," said Fitzpatrick. "A friend of mine's son's got a really good job at Oxford University on the basis of having worked for Labour Friends of Israel," Fitzpatrick said.

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Ryan became heated, accusing Jean of using an "anti-Semitic trope" and conflating a job at Oxford University with successful careers in Britain's banking sector. Ryan then abruptly ended the conversation and walked away.

"At no point did I ever say that LFI will get people jobs in banking in the City," Fitzpatrick later told Al Jazeera. "If you do talk about Palestine, it would appear you're kind of sucked into having an accusation of anti-Semitism brought against you."

Ryan has since said that it is the duty of all Labour Party members to report language that they believe to be racist or anti-Semitic, and that she believes her actions were appropriate.

Fitzpatrick's references to the group having "lots of money and prestige in the world", along with suggestions that they advance people's careers, appeared to evoke classic anti-Semitic tropes, Ryan said.

'I don't know where the line is'

But some Labour members involved in reporting the cases later had difficulty in determining what anti-Semitism was, and whether indeed the exchanges they had witnessed constituted racism.

"A difficult moment was when that woman who told us that anti-Semitism, you know, is being concocted to crush [Labour leader Jeremy] Corbyn … Is that anti-Semitic, guys, I don't know, like …?" said Jennifer Gerber, LFI director.

"I don't know where the line is any more," replied Michael Rubin, a parliamentary officer and pro-Israel activist.

Alex Richardson, Ryan's assistant, said of Fitzpatrick's case: "It is definitely on the line … If she had said the word Zionist I would have said one hundred percent. A hundred percent."

He continued: "I think if it makes you feel uncomfortable, I think that's the point which you call it out and report it, and that's why Joan convinced me to report the one yesterday because I was made to feel uncomfortable, and although nothing anti-Semitic was said I'm sure there were undertones of it and it was brought up on that context."

Richardson then said he suspected that Fitzpatrick "might be potentially banned because she said something that was anti-Semitic".

Ilan Pappe, an Israeli historian who viewed the recording of the exchanges, said: "It's [clear] in the discussion that you have filmed that the woman was not anti-Semitic. They know it. She didn't talk like an anti-Semitic person. She was a typical pro-Palestinian person who was worried about the violations of human … and civil rights.

"They are really scratching the bottom of the barrel to make a list of two and a half cases of anti-Semitism … they themselves are not totally sure that they fall into their own strict definition of anti-Semitism."

He added: "It's in a way pathetic, but it's also worrying how such pathetic evidence can be used to intimidate Jeremy Corbyn into establishing an inquiry commission and making daily confessions that he's not anti-Semitic and so on."

'Court Jew'

Earlier, Al Jazeera revealed how Jackie Walker, a black British Jew and Labour activist, was labelled an anti-Semite after attempting to debate the issues of Zionism and the inclusion of several global tragedies on Holocaust Day, in addition to the genocide during World War II. She was later suspended from the party pending investigation.

Walker told Al Jazeera that at one point during the Labour Party conference, the chair of the Jewish Labour Movement, Jeremy Newmark, allegedly called her a "court Jew".

"Now anybody who is Jewish understands what that means," she said. "If you are being abused as a black person in the same way you would be being called a house n****r."

Walker added: "I would say there is a crisis in the way the anti-Semitism is being manipulated and being used by certain parts - not just in the Labour Party but other parties and the media to discredit Jeremy Corbyn and a number of his supporters."

Jeremy Newmark denied describing Jackie Walker as a "court Jew" or saying or uttering those words in any context. He also said that he did not believe that this would be a fair or accurate description of Walker.

Israeli diplomat Masot, who was filmed during the investigation as he plotted to "take down" Britain's deputy foreign minister, resigned after that clip of Al Jazeera's investigation was released.

Al Jazeera Investigative Unit's series The Lobby can be viewed on Al Jazeera:

Episode One: Young Friends of Israel - Available online

Episode Two: The Training Session - Available online

Episode Three: An Anti-Semitic Trope - Available online

Episode Four: The Takedown - Saturday, January 14, 22:30 GMT