Conservative leader Boris Johnson urged traditional Labour voters to break the habit of a lifetime and back the Tories, in a final plea to the electorate.
He said: "Even if you have never voted Conservative before, this is your chance to be heard and I promise I will not let you down."
Voters go to the polls today in an election that could transform British politics. Mr Johnson's election message reflects Tory hopes that they could make historic gains in parts of the North and Midlands that have always voted Labour before now.
Labour, meanwhile, will learn whether the decision to break with the politics that bought it to power in the 1990s and pursue a more left-wing agenda will deliver a mandate to transform society - or give the party its fourth general election defeat in a row.
Mr Johnson hammered home the theme of his election campaign, insisting that only a vote for the Conservatives would "get Brexit done".
And he also talked up Labour leader Jeremy Corbyn's chances of becoming Prime Minister in a hung Parliament - reflecting the Conservative belief that the prospect of Mr Corbyn in Number 10 will discourage voters from backing Labour.
Mr Johnson said: "This election is our chance to end the gridlock but the result is on a knife-edge."
In a final plea to voters, Labour leader Jeremy Corbyn said the nation faced an "historic" choice and repeated a claim Labour has made throughout the election campaign - that the Conservatives plan to sell the NHS to Americans.
The Labour leader said: "Boris Johnson won't just keep everything the same, he will make it worse. He will open our NHS to takeover by American mega corporations and carry on with more cuts."
He told voters: "Tomorrow you can shock the establishment, by voting for hope. Hope for yourself. Hope for your family. Hope for your community. Hope for our NHS. Hope for our country.
"Tomorrow, vote for hope. Vote for real change."
Liberal Democrat leader Jo Swinson urged Labour supporters to vote tactically to prevent a Tory majority, effectively urging them to vote Lib Dem in English seats where Labour is third.
Opinion polls put the Conservatives in the lead as the election contest began, and they have stayed in front throughout. A recent survey by YouGov suggested Tories could gain seats from Labour including Sedgefield, Bishop Auckland and Darlington.
But Labour has closed the gap as the campaign went on - and the Tories have suffered a series of setbacks. These included Mr Johnson's refusal to look at a photo of a four-year-old boy forced to sleep on a hospital floor in Leeds, initially putting a reporter's phone displaying the picture in his pocket, in a bizarre attempt to avoid the issue.
On the final full day of campaigning, Mr Johnson suffered more embarrassment as he hid in a fridge to avoid a television reporter trying to get an interview. And a senior press officer accompanying Mr Johnson swore when approached by the journalist, unaware that the scene was being broadcast live on ITV's Good Morning Britain.
Meanwhile, Mr Corbyn attended an eve-of-poll rally in Middlesbrough, accompanied by North West Durham Labour candidate Laura Pidcock. She said: "For the person who goes out to work, every single day, spends hours and hours at work, but cannot pay their bills ... all of our energy is for them to build a different and better society."
Along with party chair Ian Lavery, candidate for Wansbeck, she played an increasingly high-profile role in Labour's campaign in the final week. It appeared to follow concern that the party's pledge of a second referendum on Brexit was alienating leave-voting Labour supporters.
Mr Lavery highlighted his support for carrying out Brexit, saying he would back leaving with Labour' deal in a second referendum.
However, Brexit continued to present a clear dividing line between the parties, with Boris Johnson pledging to take the UK out of the EU by January 31 while Mr Corbyn promised a second referendum in which he would remain neutral on the question of whether the UK should leave or not.
