University Palestine Societies have condemned former US marine Ken O'Keefe following the controversy over his comments comparing Jews to Nazis.

Six groups – at campuses in Glasgow, Leeds, Dundee, Edinburgh and Liverpool – declared that Mr O'Keefe was "not welcome to speak" at their universities.

They urged Middlesex University Free Palestine Society to distance itself from his comments, made at their Israel Apartheid Week event last month.

While admiring his stance on the wars in Iraq and Afghanistan, and his "bravery" while travelling on the Mavi Marmara ship as part of the Gaza flotilla in 2010, the societies added: "None of this can excuse the unacceptable nature of his comments."

Mr O'Keefe had claimed during the Middlesex event that Mossad was "directly involved" in the September 11 terror attacks.

The signatories added that they "stand against all forms of racism, including Zionism", but warned that "no opportunity for antisemitism" should be allowed to enter their campaigns.

Mr O'Keefe responded to the students by claiming the Palestinian solidarity movement was "rife with infiltrators and subversives posing as friends and allies of Palestine".

In a separate move, almost two dozen academics and activists called on supporters of the Palestinian cause to "disavow" anti-Zionist campaigner Gilad Atzmon.

Signatories to the letter attacking his antisemitic comments included Palestinian author Omar Barghouti and lecturers and students from SOAS.

They said supporters should "note the dangers" of backing him, and wrote that Atzmon "viciously" attacks "anyone who disagrees with his obsession with 'Jewishness'".