Nigel Farage is on course to be prime minister, according to a seat-by-seat YouGov poll which reveals the scale of Conservative implosion.

The YouGov MRP polling projection, based on a 13,000 sample taken over the last three weeks, suggests an election held tomorrow would see a hung parliament with Reform UK winning 311 of the 650 seats, 15 seats short of the formal winning line of 326.

In practice, once the Speaker and absent Sinn Fein MPs are accounted for, it would be all but impossible for anyone other than Mr Farage to secure the largest number of MP backers and thus become prime minister.

Reform UK has improved its position since the last YouGov MRP in June, when it was 55 seats short of a majority. The projection suggests 306 Reform gains, up from their current seat tally of five, which would be the biggest increase in any election in British history.

The projection of Commons seats in Great Britain puts Reform UK on 311 seats, Labour on 144 seats, Liberal Democrats on 78 seats, Conservatives on 45 seats, SNP on 37 seats and Greens on seven seats, with Plaid on six seats and three seats won by left-wing challengers.

Barely a year after Keir Starmer won a landslide, this result would see Labour lose around two-thirds of their existing seats, down from the 411 they won in last year’s general election.

This is significantly worse than the party’s 2019 result under Jeremy Corbyn when the party won 202 seats and is their lowest tally since 1931.

More than a third of Labour’s remaining seats would be in London, making them more reliant on London than any other British party is on any other nation or region.

Among the big-name casualties would be Yvette Cooper, Wes Streeting, Ed Miliband, Bridget Phillipson, Lisa Nandy and Angela Rayner.

The Conservatives would fare even worse, pushed potentially to the brink of extinction. They would lose two-thirds of their 121 seats won last year – which was already their worst result in their 190-year modern history – reducing their tally to 45 seats.

And even further back, it would be worse than any result they’ve ever suffered, all the way back to the formation of their predecessor party, the Tory Party in the 1670s.

This would put the Tories in fourth place behind the Lib Dems, and the first time they have not been one of the two biggest parties.

The Conservatives would be wiped out in both Wales and the South West, a heartland as recently as 2015, and left with just six seats in the north and one in Scotland.

Robert Jenrick, Priti Patel, James Cleverly and Mel Stride could be among the casualties. Almost 60% of their current front bench would lose their seats.

In theory, the Conservatives could line up with Labour, Lib Dems, Greens, Plaid, SNP, progressive left and Northern Ireland MPs to vote down a Farage premiership, but this is highly unlikely in practice. If they abstain, Mr Farage would still have enough MPs to become PM.

The projections suggest national vote shares of 27% for Reform UK, 21% for Labour, 17% for Conservative, 15% for Lib Dems, 11% for Greens, 3% for SNP and 1% for Plaid.

Some smaller, more recent YouGov polls have put the Reform UK total even higher.

The scale of the threat to Labour from Reform UK is laid bare in this MRP projection.

Three-quarters of Reform UK’s seats would come directly from Labour, while more than half of Labour seats would go directly to Reform UK.

The North East of England would be Reform’s strongest area with 21 of the 27 seats, followed by the East Midlands and Wales. Reform’s weakest areas are London, where they would have six out of 75 and Scotland where they would win five out of 57.

Scotland would see a resurgence of the SNP, an increase of 28 seats to 37 seats, with Labour left with nine seats.

This does not suggest Scottish Labour will be able to win control of the Scottish parliament at next year’s elections.

In Wales, Reform would have 23 seats, against Plaid’s six and Labour’s three, which implies there’s a strong likelihood of Labour losing control in the Welsh Sennedd elections next May.

Voters in Great Britain were asked by YouGov how they would vote in the event of an election tomorrow, even though one is not anticipated for three or four years. MRP projections come with a significant margin of error.

The central projection is that Reform UK gets 311 seats, but this could be as high as 342, which would deliver an overall majority, or as low as 271. The Tories could have as few as 28 seats and as high as 68 seats. Labour’s range could be from 118 to 185.