The lawyer who represented Diana, Princess of Wales in her divorce is to take on an association of university lecturers in a dispute over anti-Semitism on campuses.

Anthony Julius is representing a freelance maths lecturer who claims the University and College Union (UCU) creates a “hostile, degrading, humiliating and offensive environment” for Jews.

Ronnie Fraser, whose parents fled the Holocaust, says that after 11 years as a member he has “had enough” of its alleged anti-Semitic behaviour.

In a letter to the UCU’s general secretary, Julius, deputy chairman of the London law firm Mishcon de Reya and himself an occasional university lecturer, describes the way the academic union treats Jewish members as a “scandal”.

“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,” he writes.

“The scandal is a long-standing one… continuous with the history of the union. It persists in its inhospitable conduct – indeed intensifying it year by year, piling fresh insults upon accumulated insults to its Jewish members,” Julius adds.

The UCU is one of the biggest academic trade unions in the world, representing more than 120,000 lecturers, researchers and administrative staff who work in universities and further education colleges.

Fraser’s legal battle follows the departure of a number of Jewish members from the union in recent years over its policies towards Israeli academics and universities.

The organisation has repeatedly debated introducing an official academic boycott of Israel, but was advised by its own lawyers in 2007 that such a move would be unlawful and could not be implemented.

It is accused of allowing individuals to post hundreds of anti-Semitic comments on its internet forum for members, known as the “activists list”.

In his letter, Julius lists a string of further alleged abuses, including: “penalising” lecturers who opposed a boycott; failing to deal with Jewish and non-Jewish members’ concerns about the boycott; failing to address the resignations by Jewish members; and a decision to reject the internationally accepted definition of anti-Semitism, following a resolution at a UCU conference.

“Unable to defend itself against the charge of institutional anti-Semitism, the UCU sought instead to legislate anti-Semitism out of existence. 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,” Julius writes.

His letter on behalf of Fraser claims the problem dates back to at least 2008, since when conditions for Jewish members have “only deteriorated”.

“Further boycott resolutions have been passed; further incontinently anti-Semitic comments on the ‘activists list’ have been posted; there have been further resignations from the union by Jewish members,” he writes.

Julius, who represented Heather Mills in her multimillion-pound divorce from Sir Paul McCartney, is known for his interest in anti-Semitism. He successfully represented the American author Deborah Lipstadt in a libel battle with the Holocaust denier David Irving, and has written books on the poet TS Eliot’s hostility to Jews and on the history of anti-Semitism in England.

In his letter on behalf of Fraser, Julius demands that the UCU make an “open and unqualified acknowledgement” that it has been guilty of institutional anti-Semitism, and apologise to Jewish members and ex-members.

Fraser also wants the union to draw up a code of conduct in respect of Jewish members, and to sponsor a programme to educate academics on the dangers of anti-Semitism.

Nobody from the UCU was available to comment.