Leon Neal/PA
The Conservatives are fighting to prevent Sir Keir Starmer winning a “supermajority” as ministers appeared to concede they are heading for defeat.
Defence Secretary Grant Shapps said it would be “very bad news” for the country if Sir Keir was able to enter No 10 with his power “unchecked” by Parliament.
The Tory strategy, backed by a social media advertising campaign, is aimed at persuading would-be Reform UK voters not to risk handing Labour a majority which could eclipse even the 1997 landslide under Tony Blair.
The online advert highlights a scenario suggesting the Tories could be reduced to just 57 seats in Parliament on a 19 per cent vote share, even if Reform picked up no MPs.
Mr Shapps told Times Radio that to ensure proper accountability “you don’t want to have somebody receive a supermajority”.
He said: “In this case, of course, the concern would be that if Keir Starmer were to go into No 10 – it will either be Rishi Sunak or Keir Starmer, there’s no other outcomes to this election – and that power was in some way unchecked, it would be very bad news for people in this country.
“A blank-cheque approach, allowing someone to do anything they wanted, particularly when their particular set of plans are so vague, and they say ‘change’, but you have no idea what they actually want to change to, other than the fact that they’ve outlined plans which would cost £2,094 to every working family in this country.”
Labour has disputed the Tory claim that it would need to implement the tax rises claimed by Mr Shapps over the course of the next Parliament.
Mr Shapps added: “It’s perfectly legitimate to say the country doesn’t function well when you get majorities the size of Blair’s or even bigger, and we would say there are a lot of very good, hardworking MPs who can hold the government of the day to account and we’d say those are Conservative MPs.”
His comments came as Mr Sunak and Sir Keir prepared for a Sky News event in Grimsby where they will face questions from journalist Beth Rigby and the studio audience.
The event takes place after official figures suggested the economy flatlined in April.
Monthly gross domestic product (GDP) is estimated to have shown no growth, according to the Office for National Statistics.
Shadow chancellor Rachel Reeves said: “Rishi Sunak claims we have turned a corner, but the economy has stalled and there is no growth.”
Liberal Democrat Treasury spokeswoman Sarah Olney said: “The Conservatives have utterly failed to deliver the growth they repeatedly promised, instead presiding over stagnation and economic misery for hardworking families across the country.”
But Chancellor Jeremy Hunt said the figures showed the economy “grew by 0.7 per cent in the three months to April”.
“There is more to do, but the economy is turning a corner and inflation is back down to normal,” he said.
He said the Tories had a plan to grow the economy and cut taxes but voting Labour would “risk all that progress”.
Meanwhile, the Green Party is to publish its General Election manifesto.
A tax on multimillionaires and billionaires would be used to fund improvements to health, housing, transport and the green economy under the Greens’ plans.
Related: Labour on track to record historic 35% swing in Hartlepool
