Sir Keir Starmer has warned that Iran remains “a very serious proposition and a very significant threat” and that “we always need to bear that in mind as we go forward”.

In a further clear move away from his party’s foreign policy under Jeremy Corbyn, he told South Hampstead Synagogue members on Sunday: “We need to recognise what Iran is and what the risks are in relation to Iran.”

Sir Keir made the remarks after being asked for his thoughts on the Iran nuclear agreement and on whether the UK should be part of it.

He continued: “Of course, we need to find a way to move forwards.

“On the nuclear agreement I think it’s very important that we make progress rather than going backwards.

“But never underestimate the threat that is there from Iran.

“I think sometimes that drops off the political agenda, with Brexit over the past few years, and with Covid.”

Responding a question on whether he would “stop discriminatory targeting of Israel at the United Nations”, Sir Keir said: “Yes, where it is wrong … I’m not in a position to do so at the moment.”

But he then stressed that as an international lawyer “I believe in international law, and therefore there are elements of Israeli policy that I would disagree with and see as contrary to international law.

“It depends what the issue is.”

Nearly 400 members of the north London shul watched Sunday evening’s online event, which saw Rabbi Shlomo Levin earlier asked questions about Sir Keir’s vision for the country, the challenge of leadership during a pandemic, his continued attempts to tackle antisemitism, and on the recent criticism he had faced over his effectiveness.

On fighting antisemitism, Sir Keir said he believed “the vast majority of Labour members were not in that place” after Rabbi Levin suggested those holding anti-Jewish views  were a “significant part” of the party.

Sir Keir said: “I know some of that is there and we are dealing with it. Our job is to deal with those who are antisemitic, of course it is, and that is what we are doing.”

The Labour leader said he had been told by Jewish friends of his what it “sometimes feels like to be in those meetings.”

He said: “The vast majority of members are not that way inclined and are supportive of the action I am taking in the Labour Party and give it their full support.”

Sir Keir accepted Rabbi Levin’s claim that there “still is a mountain to climb.”  He added it would take longer than 12 months to deal with the problem.

He pointed to “the difficult decisions in terms of Rebecca Long-Bailey, the difficult decisions in terms of Jeremy Corbyn” and added he knew “what the right decision was and I took it because I meant what I said when I said I would deal with antisemitism in our party.”

Sir Keir said records showed he had spoken out about antisemitism under the previous leader – and that the charge he “did nothing” was wrong.

He said he thought it was the right decision not to quit the party – and stressed his shadow cabinet role around Brexit was “a critical role” at the time.

Rabbi Levin said he recognised the importance that the community was not defined solely by discussion around Labour antisemitism.

Asked about his vision for a future Britain, Sir Keir said he believed in a partnership between an “active state” and business and pointed to examples such as the government of New Zealand for inspiration.

He spoke of his frustration at not being able to tour the country in person because of Covid or stage regular meetings with his senior MPs in the party.

Asked if he felt like he was fighting for his party with one hand tied behind his back, Sir Keir said: “It’s very difficult. One because of the physical restrictions – it’s very difficult to show what type of person you are when you are not in the same room with people.

“And also, had it not been for the pandemic, I would have been out across the country every week with people in different communities. That’s what I want to do and I can’t do it.”

Sir Keir was later asked why he party was not ahead in the polls. He said that in the main, governments in power across Europe were supported during the pandemic.

But he then added that Labour “still have a lot of work to do” and suggested it was better to wait until the 2024 election before judging properly.

On a lighter note he said he would choose “fish balls” ahead of schmaltz herring if offered the choice.

Both Sir Keir and his wife Victoria have regularly taken part in Mitzvah Day events at the shul. He had previously told the JC he considered Rabbi Levin to be a "friend."