Last day of campaigning ahead of elections across UK
Party leaders have made a final appeal for votes before Thursday's devolved elections in Scotland, Wales and Northern Ireland, and local polls across England.
Jeremy Corbyn urged voters to "send a message" to David Cameron but appeared to back away from earlier claims that Labour would not lose seats in England, saying predictions "are not that important".
The PM said a vote for his party would secure services and keep bills down.
SNP leader Nicola Sturgeon said she was taking nothing for granted in Scotland.
The Scottish First Minister made her party's case for another five years in power at a final election rally in Glasgow. Northern Ireland's five main party leaders have debated for the last time on the BBC.
The polls will be the largest, in terms of the number of votes expected to be cast, before the next general election. All nations and regions of the UK are going to the polls on what has been dubbed "Super Thursday".
Tap here to find out which election is taking place in your area.
As well as elections to the Scottish Parliament, the National Assembly of Wales and the Northern Ireland Assembly, there will be votes for new mayors for London, Liverpool, Salford and Bristol, as well as for members of the Greater London Assembly.
More than 2,700 seats will also be up for grabs in 124 English council elections, while parliamentary by-elections will be held in Ogmore and Sheffield Brightside, both won by Labour at the last general election.
All police and crime commissioners in England will be up for re-election.
Ahead of his first UK-wide electoral test and amid renewed speculation about his leadership, Mr Corbyn is under pressure to demonstrate his party is making progress after last year's calamitous election defeat.
Mr Corbyn insisted on Tuesday that his party would not lose seats in England and would improve on its performance in 2012 - when the majority of the seats were last fought - when Labour gained almost 800 seats under Ed Miliband.
The BBC's political editor Laura Kuenssberg said Mr Corbyn's aides were now suggesting his comments had been "misinterpreted" amid the very real prospect of Labour ending the night between 100 and 300 seats worse off.
Speaking during a visit to Wales, Mr Corbyn said: "What I said was, I was not predicting any losses". With the polls now less than 24 hours away, he said "predictions are not that important".
Mr Corbyn campaigned alongside Welsh First Minister Carwyn Jones, who is seeking to hold off a resurgent Conservative Party and win enough seats to enable Labour to maintain its 17-year grip on power there.
"The Tories' failed economic policies mean there is now a multi-billion black hole to fill in this Parliament," Mr Corbyn said. "The Tories can no longer be trusted with our communities so send them a message on 5 May."
As the Welsh campaign enters its final stages, Plaid Cymru said it could call a referendum on further assembly powers if it wins power. UKIP has said it expects to win at least five seats in Wales in what it says will be a major breakthrough.
In England, the Lib Dems and the Greens are hoping to make gains while in London, all eyes are on the contest to succeed Boris Johnson as mayor, with the Conservative Zac Goldsmith trying to extend his party's eight-year rule at City Hall.
On Tuesday evening, David Cameron joined Mr Goldsmith at his final rally of the campaign, saying he was the "right man" for the capital as a whole and Londoners should not be "lab rats" for Labour's experimental economic policies.
Labour candidate Sadiq Khan urged Londoners to choose "hope over fear" and played down suggestions he would be affected by the party's recent troubles, saying: "You won't see Jeremy Corbyn's name or Ken Livingstone's name" on the ballot paper."
BBC Newsnight's political editor Nick Watt says Mr Khan plans to keep Mr Corbyn away from his victory celebrations should he prevail, and the two men would not be seen together for several days.
But Mr Khan's team said Mr Corbyn had been invited to his post-election gathering.