Annual net migration to the United Kingdom fell to 685,000 last year from a record high of 764,000 in 2022, but officials said it was too early to declare a downward trend in the number, which will be a major battleground in Britain's July 4 election.

Sunak, who surprised the nation on Wednesday by calling the vote, is trailing opposition Labour in the polls. He has repeatedly promised to reduce the number of migrants coming to Britain through both legal and illegal routes.

The figures published on Thursday show a drop on arrivals in 2022 that the Office of National Statistics revised up from 745,000.

The ONS said it was too early to say if the fall was the start of a new downward trend.

Eight years after Britain voted to leave the European Union to "take back control" of the country's borders, migration remains a hot political issue and it will be prominent in the election debate.

Net migration to Britain in 2015, the year before the Brexit referendum, was 329,000.

More of those arriving in 2023 were coming for work, which replaced study as the main reason for long-term migration, the ONS said.