Foreign Secretary Jeremy Hunt has ratcheted up the pressure on Jeremy Corbyn in the anti-Semitism row, warning he would have no moral authority to condemn terrorist attacks on British citizens if he ever became prime minister.

The Labour leader came under attack from Israeli Prime Minister Benjamin Netanyahu on Monday after it emerged that he attended a ceremony where a wreath was was laid in memory of Palestinians suspected of being behind the Munich Olympics massacre.

Mr Corbyn has acknowledged he was present at the event at the Palestinian Martyrs Cemetery in Tunisia in 2014, but said he did not “think” he was involved in the wreath-laying.

Supporters insisted he had made clear his abhorrence for the I972 Munich attack, when 11 Israeli athletes were killed, and that he condemned all terrorist acts.

However, writing on Twitter, Mr Hunt said: “If Jeremy Corbyn thinks terrorism is justified for the causes he believes in, how would he as prime minister have the moral authority to condemn terrorist murders of British citizens? Unbelievable and shocking.”

The president of the Board of Deputies of British Jews, Marie van der Zyl, poured scorn on Mr Corbyn’s claim his that he was not involved in the wreath-laying and said he needed to understand he could not “cavort” with terrorists.

“After days of being evasive, Jeremy Corbyn has now admitted attending a memorial event for the terrorist murders of unarmed athletes. How can you say he is not involved?” she told BBC Radio 4’s Today programme.

“In 1972, these are unarmed people who were attending the Olympics, they were savagely mutilated and murdered. There is no reason Jeremy Corbyn should not apologise to the widows and to the victims for this terrible massacre.

“He needs to also recognise that he can’t cavort with terrorists.”

However, Naomi Wimborne-Idrissi, a founder of Jewish Voice for Labour and a member of Momentum, claimed the row had been “cooked up” to damage the Labour leader.

“Jeremy Corbyn made absolutely clear from the first that the Munich atrocity was absolutely abhorrent to him,” she told Today.

“When he was in Tunis he was there for a pro-peace Palestinian conference. I just feel that this whole thing is yet another a cooked-up example of people trying to attribute guilt to the Labour Party leader by association.

“Jeremy Corbyn is not a supporter of terrorism. He has always condemned and abhorred every terrorist act. He is opposed to all forms of violence. This is really just barracking him, it is intimidating him the whole Labour Party.”

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

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

However, in a highly unusual intervention, he was accused by Mr Netanyahu of laying a wreath at the grave of one of the terrorists responsible for the Munich attack.

“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,” he wrote on Twitter

However, Mr Corbyn  hit back, saying the Israeli leader’s claims were “false”.

He added: “What deserves unequivocal condemnation is the killing of over 160 Palestinian protesters in Gaza by Israeli forces since March, including dozens of children.”

Earlier, during a visit to Walsall, Mr Corbyn confirmed that a wreath had been laid to -“those that were killed in Paris in 1992” – an apparent reference to assassinated PLO intelligence chief Atef Bseiso.

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