One of the country’s leading lawyers has said the Government’s newly-adopted definition of anti-Semitism is “unclear and confusing” and that any public body banning activities on the basis of it may be acting illegally.

Hugh Tomlinson QC, a top media and defamation barrister who has represented Prince Charles and A-list celebrities, presented his legal opinion on the new working definition of anti-Semitism from the International Holocaust Remembrance Alliance (IHRA) at the House of Lords on Monday.

The founding member of Matrix Chambers is known for his work on privacy and freedom of speech, playing a prominent role in the News of the World phone-hacking scandal and the saga of MPs’ parliamentary expenses.

Presenting his 10-page opinion, Tomlinson said he had been asked to consider the non-legally binding IHRA definition by Free Speech on Israel, Independent Jewish Voices, Jews for Justice for Palestinians and the Palestine Solidarity Campaign.

In it, he noted “obvious problems with the wording” of the definition, which begins with the words: “Anti-Semitism is a certain perception of Jews, which may be expressed as hatred towards Jews.” A list of illustrative examples soon follows.

“The use of language is unusual and therefore potentially confusing,” he wrote. “The phrase ‘a certain perception’ is vague and unclear in the context of a definition. The use of the word ‘may’ is also confusing… This does not work as a definition.”

He said that in some senses, the definition was insufficient. “The apparent confining of anti-Semitism to an attitude which is ‘expressed’ as a hatred of Jews seems too narrow and not to capture conduct which, though not expressed as hatred of Jews, is clearly a manifestation of anti-Semitism, for example discriminatory social and institutional practices.”

Tomlinson said the deficiencies meant that it was “obviously most unsatisfactory for the Government to adopt a definition which lacks clarity and comprehensiveness in this way,” adding that the definition was “very difficult to use as a tool”.

Another concern, he said, were the illustrative examples, such as “denying the Jewish people their right to self-determination, such as by claiming that the existence of a State of Israel is a racist endeavour”.

Tomlinson said: “Unless such a claim was informed by hatred of Jews, it would not be anti-Semitic to assert that as Israel defines itself as a Jewish state and thereby by race, and that because non-Jewish Israelis and non-Jews under its jurisdiction are discriminated against, the State of Israel is currently a racist endeavour.”

The QC also referred to the “chilling effect” on free speech in public bodies such as universities, many of which have been urged to cancel events such as Israel Apartheid Week on the basis of the new IHRA definition.

Contrary to these cancellation calls, Tomlinson said universities and colleges were duty-bound to ensure freedom of expression under Article 10 of the European Convention on Human Rights, to which the UK is subject.

“The public body would, for example, be lawfully entitled to prohibit conduct which incited hatred or intolerance against Jews,” he wrote. “It would not be lawfully entitled to prohibit conduct on the sole basis that supporters of the State of Israel found it upsetting or offensive.”

Under Tomlinson’s interpretation, universities would be obliged to allow speakers on campus such as Professor Richard Falk, the former UN Special Rapporteur for Palestine, or former Momentum vice-chair Jackie Walker, given that neither have “incited hatred or intolerance against Jews”.

Ben Jamal, director of Palestine Solidarity Campaign, said: “The message is loud and clear. Freedom of speech and human rights are values we all cherish. The law is on our side, and nothing can stop us from raising our voices to highlight the systematic denial of Palestinian human rights by the Israeli state.”