Theresa May has insisted she is "taking nothing for granted" following emphatic local election victories which have sparked predictions she is heading for a landslide in the June 8 General Election.
The Prime Minister's comment came as Labour leader Jeremy Corbyn acknowledged he faces "a challenge on a historic scale" to turn round polling figures which suggest he is headed for defeat.
Liberal Democrat leader Tim Farron said that this week's elections showed Labour was "finished" as a viable opposition to a Conservative Party which was heading for a landslide majority larger than those enjoyed by Margaret Thatcher in the 1980s.
Speaking during a campaign visit to Wolverhampton, where the Tories yesterday won the contest for West Midlands metro mayor, Mrs May said: "I'm very grateful for the support that we received in the local elections... but the question people now face in the General Election is: Who should lead the country for the next five years - me or Jeremy Corbyn?
"Not a single vote has been cast in that election yet, and none of the votes cast yesterday will count on June 8 in the General Election.
"In the minds of European politicians, there isn't a mandate to take into the Brexit negotiations.
"I'm taking nothing for granted over the next five weeks. I need support from across the United Kingdom to strengthen my hand, and only a vote for me and my team will ensure that Britain has the strong and stable leadership we need in order to ensure we get the best deal for Britain from Brexit."
Addressing supporters in Leicester, Mr Corbyn acknowledged that yesterday's results - which saw Labour shed 320 councillors and lose control of seven authorities, including Glasgow, were "disappointing", but insisted that "the gap between us and the Tories is not as great as the pundits have been saying".
He called on supporters to "seize the moment" by campaigning hard over the next five weeks to transform the party's prospects.
And he said that if Labour won, there would be "a reckoning" with big businesses and bankers who had stripped industrial assets, crashed the economy and ripped off consumers and workers.
"This election could be a great and proud moment in our national story," said Mr Corbyn.
"Don't wake on up on June 9 to see celebrations from the tax cheats, the press barons, the greedy bankers, Philip Green, the Southern Rail directors and crooked bankers that take our wealth, who have got away with it because the party they own, the Conservative Party, has won.
"We have five weeks to ruin their party. We have five weeks to have a chance to take our money back. We have five weeks to win so we can transform Britain for the many, not the few."
Speaking at the launch of a new Lib Dem policy to raise £6 billion for the NHS by putting a penny on all bands of income tax, Mr Farron said Thursday's polls gave a "crystal clear" insight into what will happen next month.
"The local elections proved that the Labour Party is finished and the Conservative Party is heading for a landslide," he said.
"On top of that, the Liberal Democrats are left as the only opposition party making progress, with a 7% increase in our vote share.
"At the moment, Theresa May is heading for a majority even bigger than the ones that Margaret Thatcher had in the 1980s, and that means all our communities, your family, your children, being taken for granted.
"There is only one opposition party left standing after Thursday - not just standing but growing - and that's the Liberal Democrats."
Meanwhile, Scottish National Party leader Nicola Sturgeon said voters in Scotland were presented with a straight choice between her party and the Conservatives, after Tories overhauled Labour as the second biggest party north of the border on Thursday.
Mrs May's party had "a good day by their standards" north of the border, but were taking votes from Labour rather than the SNP and were still securing a share of the vote in Scotland lower than Mr Corbyn's "disastrous" performance in England, said the First Minister.
"As we go into the General Election, the people of Scotland have a clear choice," said Ms Sturgeon.
"It is pretty clear that Theresa May, on the strength of support in England, is going to win the General Election, so for people in Scotland, if they want strong voices standing up for Scotland's interests and holding the Tories to account in Westminster, that can only come from the SNP."
Thursday's results were widely seen as a vindication both for Mrs May's tough line on Brexit and her decision to call a snap election.
The Conservatives effectively obliterated Ukip – which won just one seat and lost more than 100 – as voters who had deserted the Tories for Ukip returned in their droves.
But Ukip leader Paul Nuttall insisted his party was still "on the pitch" and that supporters would come back "in droves" when they saw Mrs May making concessions in Brexit negotiations.