A British academic has announced that he is taking legal action against the Universities and Colleges Union after it made the "indecent" decision to distance itself from the European Union's working definition of antisemitism.

Lawyers acting for Ronnie Fraser, the chair of the Academic Friends of Israel, have written to UCU general secretary Sally Hunt complaining that the UCU's vote breached the 2010 Equality Act's commitment.

The letter said Mr Fraser was to sue because as a result of the vote the UCU had "harassed" him by "engaging in unwanted conduct" relating to his Jewish identity.

It went on to say that without the protection of the otherwise widely-accepted definition of antisemitism, Mr Fraser now faced an "intimidating, hostile, degrading humiliating" and "offensive environment".

The lawyers added: "In simple terms, the UCU is not a place that is hospitable to Jews. This is not just a violation of equality legislation, it is also a scandal."

They said the situation was worsened by the fact that union was breaching "energetically fought-for laws against discrimination".

The letter also accused the UCU of having been "inhospitable to Jews" since its inception, because of annual Israel boycott resolutions, a failure to engage with Jewish members and the welcome it gave last year to "a confirmed antisemite" Bongani Masuku.

"This indecent, discreditable resolution was passed in active disregard of the feelings of Jewish members - a disregard amounting to a kind of inflamed contempt for all Jews other than that minority among them ready to abet a degraded and obsessive "anti-Zionist" activism," said the letter. It said Mr Fraser had now "had enough" and felt he had little option but to sue.

After the UCU vote, the union was branded "institutionally racist" by the chief executive of the Jewish Leadership Council.

Its decision was also heavily criticised this week by cabinet minister Eric Pickles, who wrote that it sent "a chilling message" to Jewish students and academics.

The UCU said Ms Hunt would not comment on the lawsuit. She has until August to respond.