Jeremy Corbyn, the Labour leader, was coming under growing pressure this afternoon from Jewish groups who wrote an open letter declaring 'enough is enough' when it comes to antisemitism in the party under his leadership.

Corbyn has said that he is 'sincerely sorry' for the pain caused by what he acknowledged were 'pockets of antisemitism' in Labour, adding that he would be meeting representatives of the Jewish community to 'rebuild' confidence in his party.

However, the organisations behind the open letter – the Board of Deputies of British Jews and the Jewish Leadership Council – are planning a protest outside Parliament later today, and Corbyn is under pressure to meet his own Labour MPs this evening.

The shadow Commons Leader Valerie Vaz urged Corbyn to attend the weekly Parliamentary Labour Party (PLP) meeting.

It had been said that Corbyn would not attend the weekly meeting, the last before the Commons takes an Easter break, but Vaz told BBC Radio 4's The Westminster Hour that he should turn up.

'I think if members of the PLP have concerns then obviously he should be encouraged to go along and address that,' she said.

Corbyn has been hit by allegations of antisemitism throughout his time as Labour leader, and the new open letter from the Jewish groups said that there has been a 'repeated institutional failure' to properly address antisemitism.

It accuses Corbyn of being unable to 'seriously contemplate anti-Semitism, because he is so ideologically fixed within a far-left world view that is instinctively hostile to mainstream Jewish communities'.

The organisations refer to Corbyn's apparently supportive message to the creator of an allegedly antisemitic mural in 2012 and his attendance at 'pro-Hezbollah rallies'.

The latest row was sparked when it emerged last week that Corbyn had posted a Facebook comment in 2012 stating that the graffiti artist Kalen Ockerman was 'in good company' over his resistance to the demolition of the supposed artwork.

Ockerman had written: 'Some of the older white Jewish folk in the local community had an issue with me portraying their beloved #Rothschild or #Warburg etc as the demons they are.'

The Jewish groups say the Labour leader has 'sided with anti-Semites' either because of 'the far left's obsessive hatred of Zionism' or 'a conspiratorial worldview in which mainstream Jewish communities are believed to be a hostile entity, a class enemy'.

The letter says that those who push antisemitic material view Corbyn as 'their figurehead' and that he is 'the only person with the standing to demand that all of this stops'.