Labour leader Ed Miliband, fresh from his triumphant keynote speech at the party conference, told the Labour Friends of Israel reception on Tuesday night: “We must have zero tolerance for those people who question the right of Israel to exist”.

He said to the crowd of 500 at the LFI fringe event in Manchester: “I utterly condemn the rocket attacks from Gaza on citizens of Israel,” and called the current “impasse” in the peace process “bleak”.

Explaining the party’s decision to back the Palestinians’ UN bid, he said: “We have got to try and find a way of encouraging moderate voices that exist in the Palestinian community, to show that some progress can be made.”

The event was also addressed by Israel’s ambassador Daniel Taub, and Shadow Foreign Secretary Douglas Alexander.

Mr Taub said he was “deeply moved” by the friendship with Israel within the Labour Party, and declared: “They ask the right questions. They don’t ask what we are against, they ask what it is that we stand for, and they try to work to advance that.”

Mr Alexander had strong words for Hizbollah, saying: “In government, we proscribed the military wing of Hizbollah here in the UK. It is time that the military wing of Hizbollah is proscribed in the European Union as well.”

Ben Garratt, LFI deputy director, speaking after the reception, said Douglas Alexander’s call for the proscription of Hizbollah was a “significant, necessary and positive development.”

Mr Alexander last week spoke out against former London mayor Ken Livingstone’s comment that rich Jews would not vote for him in mayoral elections. Mr Alexander told the London Evening Standard: “I didn’t just think it was ill-advised, I thought it was wrong.”

Next week LFI are taking Shadow Secretaries of State Liam Byrne, Chuka Umunna and David Lammy to Israel and the Palestinian territories as part of the LFI UK-Israel Economic Dialogue, which will focus on Israeli achievements in the hi-tech sector and call for greater economic co-operation between the UK and Israel, and between Israelis and Palestinians.

Labour Friends of Palestine and the Middle East also held a fringe session in Manchester on Sunday at which Mr Miliband and Mr Alexander also spoke. Other speakers included Islington North MP Jeremy Corbyn, Labour MP for Wigan Lisa Nandy, and Palestinian Ambassador Manuel Hassassian.

Mr Hassassian told the audience of 300 that there was great support for Palestinians from the British people, and that the government must reflect that.