Shadow chancellor John McDonnell has revealed he is “worried and saddened” about the prospect of the Labour Party splitting over the anti-Semitism row.
Mr McDonnell told the New Statesman he wanted to avoid a split “at all costs” and was happy to talk to unhappy MPs.
The party has been at war with itself over the issue throughout the summer.
Earlier, former Home Secretary Lord Blunkett called for “seismic change” after veteran MP Frank Field resigned the whip in protest at the leadership.
Mr Field’s resignation followed a summer of stories about anti-Semitism and the Labour Party.
Labour leader Jeremy Corbyn was criticised for his presence at a wreath-laying ceremony in Tunisia in 2014, which was said to have honoured the perpetrators of the 1972 Munich terror attack.
Later, footage emerged from 2013 of Mr Corbyn saying a group of British Zionists had “no sense of English irony”.
Former chief rabbi Lord Sacks branded his comments as “the most offensive statement” by a politician since Enoch Powell’s Rivers of Blood speech.
He accused Mr Corbyn of being an “anti-Semite” – with the Labour leader saying he was “more careful” with language now.
In the New Statesman interview, Mr McDonnell said: “I think there are people who are willing to leave the party”.
“I don’t understand why there is this sort of pre-emptive move to split off,” he went on.
“So I’m worried and I’m saddened by that and I think that open door is always there to prevent that happening, because any split is automatically damaging.”
He continued: “I lost a debate for 30 years, and I stayed within the party.
“If you’re having people like the SDP [who split from Labour in the 1980s] standing in particular constituencies, it takes votes away from Labour.
“So the issue for me is I’d want to avoid at all costs a split if we can.”
Writing in the Daily Telegraph on Saturday, Lord Blunkett urged a rethink of the “so-called Corbyn project” and called on the party to abandon “the recent return to bullying and thuggery experienced in the 1980s”.
He told the party to “belatedly get its act together” and “demonstrate the leadership qualities which have been lacking”.
Mr Field quit the Labour group at Westminster over what he called the party’s “tolerance” of anti-Semitism and a “culture of nastiness”.
But Mr McDonnell said: “My view is this. I want it resolved quickly.
“I think we can come out of it as the anti-racist party that we are tackling the real issues.
“I don’t want to live in a society where synagogues are attacked, or where Jews graveyards daubed with swastikas or worse, Jewish children having to have security at their schools.”
But he stopped short of calling for Labour to adopt the International Holocaust Remembrance Alliance guidelines on anti-Semitism, the magazine said.