While Labour is expected to win a thumping national majority on July 4, leader Keir Starmer's refusal to back an unconditional ceasefire in Gaza has caused a split with once-loyal Muslim supporters.
That rift could influence the result in marginal seats that have a sizeable Muslim population, such as Keighley and Ilkley in Yorkshire.
Around four in five UK Muslims voted Labour in 2019, reinforcing the historic links that were forged after the mass migration of workers from Pakistan in the 1950s and 1960s.
But recent polling suggested around one in five of those voters are set to defect, further weakening the country's traditional voting blocs.
"It's definitely an issue... but I'm quite hopeful as the election campaign goes on that I will retain a large part of the Muslim vote where it's a particular concern," said Labour candidate John Grogan at his Keighley campaign office, surrounded by boxes of "Vote Labour" posters and flyers.
"Here in Keighley, the mosques are taking a neutral position. In some towns across the north of England, the mosques are saying, 'don't vote for either of the main parties'," he told AFP.
A robust doorstep debate on the campaign trail revealed the depth of feeling, with Grogan stressing to a local resident that Labour in power would "respect the power of the international court" and recognise a Palestinian state.
He also highlighted his vote against the Iraq war while an MP in 2003.
"Keir Starmer is going to be your leader though. Whatever Keir Starmer says is what you follow," the sceptical voter, who wished to remain anonymous, said from his front door.
"The only one who is speaking at the moment is George Galloway," he added, referring to the veteran firebrand politician who recently became an MP in a similar seat by running on the issue.
"Well, he's not going to get things done mate," replied Grogan. "I want to be in parliament the day that Britain, France and Germany recognise a Palestinian state. We're committed to doing it."
While losing support among some in the Muslim community, others pledged their support for Grogan as he walked the streets campaigning, aided by a Bengali cricket team.
'Very, very angry'
The Conservatives could theoretically hold the seat if enough voters desert Labour for other candidates, such as independent Vasim Shabir, who has made Gaza the focal point of his campaign.
"Gaza has galvanised a lot of people who were either politically apathetic or politically asleep," Shabir told AFP outside a town centre kebab shop that was flying his campaign flag.
"We want to be disrupters. I want to alter the election," he added, explaining his goal was to prevent a Labour victory.
Solicitor Shaid Iqbal, a leading figure in the town's Muslim community, said people were "very, very angry".
"They're angry at both parties. But the fact is, Labour more, because they thought that Labour was a party which would stick up for human rights, speak up against atrocities," he added.
"They've let the public down."
Labour strategists said the issue lost them votes during May's English local elections, but such is the disillusionment at the ruling Conservatives, the party is still expected to win in Keighley and Ilkley.
However, Shabir said demographic divides within the Muslim community meant that Labour's relief may be temporary.
"The older generation, who don't have access to TikTok and social media, are still pretty much loyal to Labour," he said.
"The younger generation, British-born Pakistanis and Bengalis in this constituency, overwhelmingly do not want to vote for Labour.
"I think they are going to lose the vote for a generation to come," he said, adding there were "a lot of discussions going on" between independent candidates about forming a new party.
