Prime Minister Boris Johnson, who gambled his premiership by triggering the vote, has sought to focus on his pledge to "get Brexit done" throughout the campaign.

Labour leader Jeremy Corbyn, his rival in the race to No.10, has instead tried to highlight his party's credentials on the health service and other domestic issues.

Johnson arrived at Central Methodist Hall in Westminster on Thursday morning to cast his vote, bringing dog Dilyn along with him.

Labour Party leader Jeremy Corbyn was greeted by a small number of supporters as he arrived to cast his vote in Islington - and a protester dressed as Sesame Street character Elmo.

In Scotland, First Minister Nicola Sturgeon was joined by her partner Peter Murrell, as well as the SNP's Glasgow East candidate David Linden, in voting in Uddingston, South Lanarkshire.

Lib Dem leader Jo Swinson and her partner Duncan Hames were also out early to vote at a school in Glasgow.

It comes as the polls have narrowed in the final week of what has largely been a tame campaign - with few gaffes and many stage-managed visits.

On Monday Johnson came under fire for his alleged lack of empathy when he pocketed a journalist's phone when asked to view a photograph of a four-year-old boy who was forced to sleep on a hospital floor.

The following day, however, Labour's campaign was rocked when a member of the shadow cabinet was revealed to have poured scorn on Corbyn's election chances in a leaked recording.

A terrorist attack on London Bridge - which echoed a similar incident in the middle of the 2017 election - briefly disrupted the campaign, but quickly turned political as the Tories and Labour exchanged blows over how to deal with such threats.

The third general election in less than five years has been largely dominated by the 2016 vote to leave the European Union, with Labour pledging to give voters another say in a second referendum, while the Tories have vowed to take the UK out of the EU next month.

The final Ipsos Mori poll before votes are counted suggests the Tories will win - but the result remains unpredictable, with one in four voters still saying they could change their mind.

The polling research for the Evening Standard newspaper puts Conservatives on 44 per cent, Labour 33 per cent, Liberal Democrats 12 per cent, Greens three per cent and Brexit Party on two per cent, while "others" would take a vote share of six per cent.

Voter turnout, however, could play a major role in the election outcome with rain, wind and chilly temperatures forecast for much of the country.

In a final plea to voters on the eve of polling day, Johnson warned the election remained on a "knife edge" but said it represented a chance to "end the gridlock".

Corbyn, meanwhile, stressed the "very profound" issues at stake in Thursday's vote.

"You go down the road of Boris Johnson, a sweetheart deal with Donald Trump, we break off any serious relationship with Europe," he said.

"Or you go down the Labour way, which is the adult, responsible way, of negotiating a settlement which we will all live by, and I will make sure is carried out in a future relationship with Europe."

Liberal Democrats leader Jo Swinson said the polls showed it was still "absolutely possible" to deny the Tories an overall majority through tactical voting.

Brexit Party leader Nigel Farage, speaking in Doncaster, said he was hoping for "very, very heavy rain" in the town on Thursday, in the belief it would depress the votes of the other parties.

Australian Associated Press