Opinion polls show the centre-left Labour Party is set for a big win in Thursday's vote that would end 14 years of Conservative government and hand Starmer, 61, the keys to the Prime Minister's Number 10 Downing Street office on Friday morning.
You Gov's final seat projection published on Wednesday put Labour on track to win a majority of 212 seats, the largest of any party in modern history.
Both Starmer and Conservative Prime Minister Rishi Sunak, 44, kicked off the last day of campaigning before polls open warning voters of dire economic consequences if the other man wins.
But, facing predictions of the worst result in the party's history, the Conservatives turned their focus to damage limitation, saying they needed to hang on to enough seats to provide an effective opposition to a Labour government.
"I totally accept that where the polls are at the moment means that tomorrow is likely to see the largest Labour landslide majority, the largest majority that this country has ever seen," Conservative minister Mel Stride told the BBC.
"What therefore matters now is what kind of opposition do we have, what kind of ability to scrutinise government is there within parliament."
Asked about Stride's comments, Sunak told ITV: "I'm fighting hard for every vote".
Rupert Murdoch-owned British tabloid newspaper The Sun endorsed Labour and Starmer on Wednesday, saying in an editorial published online: "It’s time for a change."
"The insurmountable problem faced by the (Conservatives) is that - over the course of 14 often chaotic years - they have become a divided rabble, more interested in fighting themselves than running the country," the newspaper, which has backed the Conservatives at every election since 2010, said.
GET THE VOTE OUT
Labour's final campaign push focused on their fear that voters could see the result as a foregone conclusion and stay at home during polling on Thursday, or register protest votes with smaller parties.
Starmer said Stride's comments were an attempt to lure wavering voters into not casting their ballots after polling opens at 6am (local time).
"I say: if you want change, you have to vote for it. I want people to be part of a change. I know there are very close constituencies across the country," he told the BBC.
"I don't take anything for granted, I respect the voters, and I know that we have to earn every vote until 10 o'clock tomorrow night and we will do that."
Starmer's campaign has been built around a one-word promise of 'change', tapping into discontent at the state of Britain's stretched public services and falling living standards - symptoms of a sluggish economy and political instability.
Sunak has sought to persuade voters that his 20 months in charge have set the economy on an upward path after the external shocks of Covid-19 and the war in Ukraine, and drawn a line under years of turmoil overseen by his Conservative predecessors.
He says Starmer will have to put up taxes to implement his agenda for change and the bigger Labour's win, the more emboldened Starmer would be to raise taxes beyond those he has already outlined.
Having failed to close Labour's roughly 20-point opinion poll lead, Sunak turned to former Prime Minister Boris Johnson - the man he helped turf out of office in 2022 - inviting him to speak at a late night Conservative Rally on Tuesday.
Johnson, one of British politics' most recognisable figures and the man who delivered the party a landslide win in 2019, made his first big public appearance of the campaign with a speech which listed many of his own achievements and gave little personal endorsement to Sunak.
"None of us can sit back as a Labour government prepares to use a sledgehammer majority to destroy so much of what we have achieved," he said.
PUNISHING GOVERNMENT
If the opinion polls are correct, Britain will follow other European countries in punishing their governments after a cost of living crisis. Unlike France, it looks set to move to the centre left and not further right.
Labour has held a poll lead of between 15 and 20 points since shortly after Sunak was chosen by his lawmakers in October 2022 to replace Liz Truss who resigned after 44 days, having sparked a bond market meltdown and a collapse in sterling.
Starmer, the former chief prosecutor of England and Wales, took over Labour from veteran socialist Jeremy Corbyn after it suffered its worst defeat for 84 years in 2019, and dragged it back to the centre.
At the same time, the Conservatives in Westminster have imploded, ripped apart by scandal under Johnson and the rancour that followed the vote to leave the European Union, and a failure to deliver on the demands of its broad 2019 voter base.
While Johnson destroyed the party's reputation for integrity, Truss eroded its long-held economic credibility, leaving Sunak to steady the ship. During his time inflation returned to target from its 41-year high of 11.1% and he resolved some Brexit tensions, but the polls have not budged.
Sunak's election campaign has been hit by a string of gaffes. He announced the vote in driving rain, an early departure from a D-Day event in France this year angered veterans and allegations of election gambling among aides reignited talk of scandal.
The unexpected arrival of Nigel Farage to lead the right-wing Reform UK has also eaten into the Conservatives' vote, while the centrist Liberal Democrats are predicted to fare well in the party's traditional affluent heartlands.
