Theresa May will order the Conservatives to work "flat out" for victory, warning her supporters that opinion poll leads over Jeremy Corbyn's Labour could be wrong.
She will tell would-be MPs that they can take nothing for granted, despite the strong performance in last week's local elections.
Pointing to the Brexit referendum and the 2015 election result, the Prime Minister will say that public votes can throw up surprise results so the Tories can leave "no stone unturned" in pursuit of success on June 8.
In the latest sign of the Tory strategy of putting Mrs May's leadership at the centre of the party's appeal to voters, the Prime Minister will refer to "my local candidates" - rather than the Conservatives.
Speaking at a campaign launch for parliamentary candidates in London and the South East, she will say: "The local elections are now behind us. It's time to focus on this crucial General Election campaign.
"And we can take absolutely nothing for granted."
In a warning against complacency, she will point to recent upsets at the ballot box, saying she had learned "never to predict an election result".
"How many times over the past few years have the polls got it wrong? They got the 2015 election wrong. They got the EU referendum wrong.
"And Jeremy Corbyn was a 200-1 outsider to be Labour leader."
Using her familiar campaign slogan, Mrs May will say: "A vote for me and my team is a vote to secure strong and stable leadership through Brexit and beyond.
"A vote for me and my team will strengthen my hand in the Brexit negotiations.
"A vote for me and my team will lock in economic security for our whole country.
"The alternative is to risk making Jeremy Corbyn our prime minister."
Giving her instructions to would-be MPs, she will tell them to "go out there and earn the support" of voters.
"We must take nothing for granted, leave no stone unturned, no door un-knocked on," she will say.
"It is only by working flat-out, every day, from now to 8 June that we can gain the trust of the British people and earn their support on polling day."