Jeremy Corbyn has clashed with the Israeli prime minister as a row escalated over the Labour leader’s presence at an event which included the honouring of a Palestinian suspected of involvement in the Munich Olympics massacre.

Benjamin Netanyahu said Mr Corbyn deserved “unequivocal condemnation”, accusing him of laying a wreath on the grave of one of those behind the 1972 atrocity in which 11 Israeli athletes were killed, at a Tunisian cemetery in 2014.

The right-wing Likud leader also criticised the UK Labour leader for drawing parallels between Israeli actions against Palestinians and Nazi atrocities.

Mr Corbyn hit back in the Twitter spat, saying the accusations were “false” and blasting Mr Netanyahu’s policies in Gaza.

Mr Corbyn had earlier said he had been present when a wreath was laid to “those that were killed in Paris in 1992”, but he did not “think” he was involved in laying it during a controversial visit to the Palestinian Martyrs’ Cemetery.

Labour said he attended the event only to remember victims of a 1985 Israeli air strike on Palestinian Liberation Organisation (PLO) offices in Tunis.

Israeli secret service Mossad was accused of killing terrorists behind the Olympics attack, including Atef Bseiso, a PLO intelligence chief, who was killed in the French capital in 1992.

Writing on Twitter, Mr Netanyahu said: “The laying of a wreath by Jeremy Corbyn on the graves of the terrorist who perpetrated the Munich massacre and his comparison of Israel to the Nazis deserves unequivocal condemnation from everyone – left, right and everything in between.”

Mr Corbyn was quick to deny the claims, saying: “What deserves unequivocal condemnation is the killing of over 160 Palestinian protesters in Gaza by Israeli forces since March, including dozens of children.”

The Labour leader faced calls to quit on Monday over his controversial visit to the cemetery four years ago.

The row erupted after the Daily Mail published pictures of the Labour leader holding a wreath in the cemetery, which it said were taken in front of a plaque honouring the founder of Black September.

The Palestinian terrorist group killed 11 Israeli athletes at the 1972 Munich Olympics.

Asked about the incident during a visit to Walsall on Monday, Mr Corbyn said: “A wreath was indeed laid by some of those who attended conference to those that were killed in Paris in 1992.

“I was present when it was laid. I don’t think I was actually involved in it (laying it).

“I was there because I wanted to see a fitting memorial to everyone who has died in every terrorist incident everywhere because we have to end it.

“You cannot pursue peace by a cycle of violence. The only way you pursue peace is a cycle of dialogue.”

Criticism came from the Conservatives and from within Mr Corbyn’s own party.

Jewish Labour MP Luciana Berger said: “Being ‘present’ is the same as being involved.

“When I attend a memorial, my presence alone, whether I lay a wreath or not, demonstrates my association & support.

“There can also never be a ‘fitting memorial’ for terrorists. Where is the apology?

The widows of the Israeli athletes said they were “extremely disturbed” by claims about the visit.

Conservative Party chairman Brandon Lewis said the row showed Mr Corbyn was “unfit for senior public office, never mind his position as the official Leader of Her Majesty’s Opposition”.

Writing in Tuesday’s Daily Mail, Mr Lewis said that “decent” Labour members should be questioning whether Mr Corbyn should continue to lead “a party that has long fought to promote anti-racism and social justice”.

Mr Lewis added: “At such a crucial time for Britain’s future, this cannot continue. I feel only foreboding.”

A spokesman for Mr Corbyn said: “Jeremy did not lay any wreath at the graves of those alleged to have been linked to the Black September organisation or the 1972 Munich killings.

“He of course condemns that terrible attack, as he does the 1985 bombing.”

Mr Corbyn said last year he had spoken at the conference and “I laid a wreath to all those that had died in the air attack that took place on Tunis, on the headquarters of the Palestinian organisations there”.

Writing in the Morning Star at the time of the visit, Mr Corbyn said wreaths had been laid not only at the memorial, but also “on the graves of others killed by Mossad agents in Paris in 1991”.

The pictures emerged amid continuing controversy over Labour’s refusal to adopt in full an international definition of anti-Semitism, including a list of examples of anti-Semitic behaviour.

Labour launched a consultation with Jewish groups over the code, after protests that the version agreed by the party’s ruling National Executive Committee omits four examples relating to criticism of the state of Israel.

Mr Corbyn said on Monday that Labour’s version of code was the “most sophisticated” of any political party.