A professor had his workshop on conflict unlawfully cancelled by one of Britain's biggest unions because he is from Israel, a court has heard.

Prof Moty Cristal had been invited to lead a session for managers and unions, entitled The Role of Negotiation in Dealing With Conflict, at the Manchester Mental Health and Social Care Trust last May.

However, he was told the event had been cancelled by the workshop organisers Unison on the grounds that it is their policy, and the policy of the Trades Union Congress, "to support the Palestinian people" and his presence would compromise this commitment.

Two weeks before Cristal was due to give the seminar, the 45-year-old was told that "to invite a prominent Israeli negotiator would contradict Unison and TUC policy".

Cristal, from Tel Aviv, is now suing Unison, along with the health trust, for £26,000 in damages for racial discrimination.

Although the health trust has a long-standing boycott of goods produced in the Occupied Territories, Cristal's lawyers said there is no lawful justification to ban the professor from the talk just because he is from Israel.

Both Unison and the health trust deny any wrongdoing.

Dinah Rose QC, representing Cristal, told the hearing at Central London County Court that her client has been the victim of what amounts to racial discrimination.

She said: "He is an Israeli national and of Jewish ethnic origin. This case is very important to Professor Cristal.

"It is also a case of considerable general public importance, because it raises the issue of circumstances in which it is unlawful both for public or for private bodies to seek to boycott people because they are Israeli or because of their association with the Israeli state.

"No policy of either Unison or the TUC has been identified to us or disclosed to us. We are aware that it is TUC policy to boycott goods which have been produced in Palestinian occupied territories. We have not been shown any policy of Unison or been told how it would be contradicted by Professor Cristal's attendance."

Unison previously confirmed that its members had requested that Cristal's invitation be withdrawn and would boycott the event if he attended, but the union is opposed to "a direct boycott of all Israeli people".

Cristal is now seeking his original £3,500 payment for the talk as well as additional sums for injury to feelings and aggravated damages.

The case is expected to finish on 13 September.