Voting began at 7 a.m. and vote stations were set to close at 10 p.m. (local time). The announcement of results will begin on Sunday night, after the rest of the European Union member states have gone to the polls over the next three days.
Britain is split into 12 regions for the elections, including 9 in England and one each in Scotland, Wales and Northern Ireland. British voters will elect 73 members to the European Parliament (MEPs) out of the 751 for a term that starts on July 2, the BBC reported.
The election was being held in a climate of widespread voter apathy over the uncertainty surrounding Brexit as the House of Commons has rejected Prime Minister Theresa May's deal three times and there had been calls for a second referendum.
The results from Britain will show whether the newly launched Brexit Party, founded by veteran eurosceptic Nigel Farage, will win the largest number of the 73 British seats in the European Parliament as is forecast.
In Liverpool, England, retired teacher Pauline Roy said she would vote for opposition Labour Party.
Roy said she had considered spoiling her ballot paper. "But upon reflection, I have decided I must vote (for) Labour, mainly because I trust them, more than any other party, to deliver Brexit."
Roy, who voted to leave in the 2016 referendum, said, "More than anything else, I want this issue sorted so that we can address the issues, which are running down our country."
Initially, the elections were not planned as Britain prepared to leave the EU on March 29. But at the European summit in April, the British government and the European Council agreed to delay Brexit until October 31.
The UK is obligated to participate in the elections as it is still a member of the EU. But it's uncertain for how long British MEPs will continue because of the uncertainties over Brexit.
The elections are the 9th time Britain has elected MEPs to the European Parliament.
Theresa May's Conservatives in the European Parliament have 18 seats, the same as Jeremy Corbyn's Labour Party, followed by Farage's Brexit Party with 14 seats, which earlier belonged to the UK Independence Party.
The rest of the seats are held by others, including two of Nicola Sturgeon's Scottish National Party and one of Vince Cable's Liberal Democrats.
( With inputs from IANS )