The University and College Union travelled a “dangerously slippery slope” from criticism of Israel to “plain old antisemitism”, an employment tribunal has heard.

Jeremy Newmark, Jewish Leadership Council chief executive, said the UCU’s proposed academic boycott of Israel had been “hugely concerning” for the Jewish community.

Mr Newmark gave evidence at the employment tribunal brought by maths lecturer Ronnie Fraser, who is challenging the UCU after its rejection of a widely-accepted definition of antisemitism last year.

That rejection had marked a “tipping point”, Mr Newmark told London’s Central Employment Tribunal on Tuesday.

“That was the moment we began to talk of institutional antisemitism.”

During two-and-a-half hours of cross-examination, Mr Newmark regularly clashed with the UCU’s defence lawyer, Antony White QC.

Mr White accused Mr Newmark of making “a series of false accusations” in his submitted witness statement.

Mr Newmark said that at the union’s congress in 2008 he had been “targeted” by UCU officials who saw he was wearing a kippah and stopped him entering the conference hall.

Mr White said: “What, in fact, happened was you were trying to push your way in, despite having the wrong badge.”

Mr Newmark responded: “It’s very easy to use the stereotype of a pushy Jew. That’s not what happened. Nobody else was stopped from going in. They knew me.”

Mr White argued that some Jewish members of the union had backed the boycott. The tribunal heard how activists from Jews for Justice for Palestinians had been supportive of the policy.

Mr Newmark rejected those Jewish views as having been “grossly, disproportionately magnified” by UCU. The Jews backing the boycott were “a tiny group of people who only identify as Jews to take political positions in debates on Israel. These people are not engaged in Jewish life in any way,” he said.

Those Jews supporting the UCU stance “could not be more irrelevant in Jewish life in this country. Most British Jews are deeply disturbed by what they have seen in British academia”.

The tribunal heard how Mr Newmark and other communal figures, including Lord Janner, had held a secret meeting with UCU general secretary Sally Hunt in June 2007.

Mr Newmark said the meeting had been “informal and relaxed”.

Mr White said Ms Hunt had described at the meeting how she did not believe an academic boycott of Israel was what UCU members wanted.

“Our understanding,” said Mr Newmark, “was that she was disappointed to be caught as the meat in the sandwich” between opposing factions within the union and the supporters of Israel.

Mr Newmark said there had been a lack of sensitivity from the UCU leadership at that time over the use of classic antisemitic tropes by union members.

“There was language that echoed age-old antisemitic conspiracy theories. There was a misunderstanding from Sally. We felt it in that room and we made that point.”

Jewish students had reported how lecturers had delivered a “drip feed” of information on the Middle East conflict and the proposed boycott, said Mr Newmark.

UCU activists, including Tom Hickey and Sue Blackwell, had “roamed campuses promoting an agenda which created hatred and antisemitism,” he alleged.

Former MP Denis MacShane gave evidence on Wednesday. He chaired the All-Party Parliamentary Inquiry into Antisemitism and said that the EUMC definition had been “very helpful” and “invaluable” to those combating hatred.

After the union rejected the definition, Dr MacShane “felt horrified for all the Jewish lecturers who felt obliged to resign”.

Dr MacShane likened the boycott calls to the persecution of Jews in Nazi Germany, and said he felt the union had “gone down an antisemitic road”.