Labour’s support among Muslim voters has collapsed by almost a third since the last election following anger over Sir Keir Starmer’s stance on Gaza.

A shock new poll has found that 60 per cent plan to support the party later this year, compared to 86 per cent who cast their ballots for Jeremy Corbyn in 2019.

The survey, published on Monday, sent shockwaves through Labour with one MP warning it showed the party has become “toxic” with Muslims.

It will add to pressure on Sir Keir to change his stance on Gaza and call for a full-blown ceasefire, as demanded by many of his backbenchers.

The Labour leader has faced growing calls to about-turn, with some of his MPs facing challenges from pro-Palestine candidates at the next election.

He has so far refused to relent, though he has notably toughened up his rhetoric in recent weeks, calling on Israel to “end its bombing campaign”.

The polling, carried out by Survation for the Labour Muslim Network, found that support among Muslim voters has dropped by 26 per cent since 2019.

John McDonnell, a former shadow chancellor, said the findings made “sombre reading” but reflected what campaigners were hearing on the ground.

Mish Rahman, a member of the National Executive Committee, Labour’s ruling body, added: “These findings are deeply worrying but unsurprising. For months I have been alarmed by the Labour leadership’s willingness to turn a blind eye to Islamophobia within the Party. 

“It’s clear that the leadership is not taking this issue seriously. This poll should be a wake-up call to change course before it’s too late.”

He accused Sir Keir of showing a “sheer disregard for Palestinian lives” and of overseeing “mistreatment” of prominent Muslim MPs within the party.

One Labour MP complained that the party had been “outflanked” by the Tories, which was now taking a tougher stance on ending the war in Gaza.

They told ITV: “We told the leadership exactly what was happening and how our constituents were feeling about Gaza and they just weren’t interested and now we can see that the Party is becoming toxic among the British Muslim community.”

Lord Cameron, the Foreign Secretary, suggested last week that the Government could recognise a Palestinian state when the conflict is over. He also said that he is “determined” to secure a 40-day pause in the fighting which can be turned “into the ceasefire, into the process, into the solution”.

In contrast, Sir Keir has angered Labour MPs after dropping a Corbyn-era policy to recognise a Palestinian state immediately upon entering office.

He faced the biggest crisis of his leadership last November when 56 of his own MPs defied the whip to vote in favour of a ceasefire in Gaza.

The Labour leader was rocked by 10 front-bench resignations, including eight shadow ministers, who quit so they could back the motion.

Anger is also still simmering over comments he made in October, when he appeared to say Israel had the right to withhold power and water from Gaza. Sir Keir has since insisted that he did not mean to endorse such actions, and that he was answering a wider question about Israel’s right to defend itself.