LONDON (Reuters) - Celebrations by Britain's Labour over local election victories were tempered on Friday by concerns that Muslim voters had turned against the opposition party over Gaza, a trend that could hamper its fortunes at a national poll this year.

Labour leader Keir Starmer has struggled to bring his party with him on the Gaza conflict despite bowing to pressure this year to call for a lasting ceasefire, with some critics urging him to toughen his line on Israel.

But despite seeing a drop in voters for Labour in places with large Muslim populations in southern and northern England, one lawmaker said he saw it more as a protest vote, which would not necessarily be replicated in the national election.

Speaking after his party won a parliament seat in northern England and control of several councils across England, dealing a huge blow to the governing Conservatives, Starmer acknowledged Gaza had had an impact on Labour support in some areas.

"Look, there are some places where that's a very strong factor and I understand that, respect that," he told reporters.

"Where we have lost votes, we will earn them back through hard work, just as we have done on many other issues, but I don't think that that can really shut out the fact that this is a very good set of results for the Labour Party."

Britain's leading pollster John Curtice said from the earliest results it looked as though Labour's support was down by eight points since last year in areas where more than 10% of people identify as Muslim.

With his Labour Party well ahead in the polls before the national election, Starmer's approach to the conflict has almost been in lockstep with the government's, carefully calibrated to say Israel has the right to defend itself but saying the level of death and destruction in Gaza has been intolerable.

His position is also shaped by his pledge when appointed Labour leader in 2020 to stamp out antisemitism in the party after his leftist predecessor Jeremy Corbyn repeatedly came under fire by critics over his response to allegations of antisemitic abuse.

OPEN DIVISIONS

The divisions in Labour blew open late last year when several members of Starmer's policy team quit their roles to vote for a ceasefire in Gaza.

Since then he has been forced to pull the party's support for a candidate at an election in northern England earlier this year who had been recorded espousing conspiracy theories about Israel. That opened the way for left-wing maverick George Galloway to win a seat in parliament on a pro-Palestinian platform.

At Thursday's local elections, Labour lost control of the council in Oldham, a town in northwestern England with a sizeable Muslim population, after two former Labour councillors left the party to run as independents over Gaza.

The Labour leader of the council in nearby Bolton said some results had been affected by the war in Gaza, after voters elected a Green Party councillor for the first time.

"Getting a backlash as a result of the Gaza crisis was not wholly unexpected," Nick Peel, the Labour leader of the Bolton council, told the Bolton News.

But one Labour lawmaker in northern England said he was confident voters would look at more domestic issues at the general election, which Prime Minister Rishi Sunak said he expects to take place in the second half of the year.

"It's all come down to Gaza in some of these areas," he said on condition of anonymity. "So there has been an issue. Do I think that will be replicated in a general (election)? No, because I like to think people will vote on more than just the one issue."

(Reporting by Elizabeth Piper, Editing by William Maclean)

By Elizabeth Piper