The Conservatives face losing their Commons majority if local election results are replicated at a general election, according to a Sky News projection.

Analysis suggests that it would mean a hung parliament with Prime Minister Boris Johnson’s Tories remaining the largest party at Westminster but falling 48 seats short of an overall majority.

The projection is based on local election results from 1,700 wards and an analysis of change in vote share since 2018 across 87 local authorities.

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It predicts that the Conservatives would have 278 seats, just seven more than Labour on 271.

The figures come after Mr Johnson admitted it was a “tough night” for his party after it lost some key local councils in London to Labour – though the opposition party had mixed results outside the capital.

Some local Conservative leaders were blaming the prime minister for shock losses as partygate and the cost of living dominated comments at the doorstep.

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One southern Tory MP told Sky News: “It’s pretty grim. The PM is to blame, no one else, and there are now 19 Tory London MPs who will be baying for blood. The PM is killing our traditional vote.”

But Mr Johnson’s allies warned it was not time to change the leader as they insisted Labour gains fell short of what was needed for the party to secure a general election victory.

The PM said: “We’ve had a tough night in some parts of the country, but on the other hand, in other parts of the country, you’re still seeing Conservatives going forward and making quite remarkable gains.”

He said the local election results were “certainly mixed” after the Tories lost Wandsworth, Margaret Thatcher’s “favourite council”, Westminster and Barnet to Labour.

However, Labour gains in the rest of England were more modest.

The party was also buffeted by the announcement on Friday that leader Sir Keir Starmer will be investigated by police in Durham over “beergate” – the allegation that he broke lockdown rules while drinking with colleagues in April last year.

Local elections live: Lib Dem gains could spook Tory MPs weighing up PM’s future

The Conservatives were dealt a blow in Somerset where the Lib Dems won a strong majority, taking back control of the council 13 years after losing it to the Tories.

Sir Keir Starmer, speaking from Barnet on Friday morning, said the results represented a “massive turning point for the Labour Party”.

“From the depths in 2019 we are back on track now for the general election, showing what the change that we’ve done, the hard change that we’ve done in the last two years, what a difference it has made,” he added.

Emily Thornberry, Labour’s shadow attorney general, told Sky News: “We still have a mountain to climb, we’re not pretending that we don’t.

“We’re back – and we’re on the right path to becoming the next government.”

Labour sources were particularly jubilant about grabbing the Tories’ “jewel in the crown” in Wandsworth, the London borough which has been held by the party since 1978.

But Iain Duncan Smith, the Conservative MP and former party leader, told Sky News: “No mid-term council election is ever positive in a way… You really can’t extrapolate from here.”

But he admitted that “London has not been good”.

Outside the capital, Labour was triumphant in the new Cumberland unitary council, which covers Tory-held seats, and took the bellwether council of Southampton from the Tories.

But in high profile places where Labour needed to make advances – such as Hartlepool, Peterborough, Redditch and Ipswich, the party failed to take those councils.

Maidstone, whose MP is Conservative, saw Labour and the Greens pick up one seat each to pull the Tory-run council into no overall control.

While the Conservatives have seen a substantial drop in support in the south of England, Labour has seen a larger drop in the north.

A rise in Lib Dem support across England has seen the party winning Hull from Labour, gaining from the Tories in Merton and in West Oxfordshire where former David Cameron previously had his constituency.

In England, there were more than 4,000 seats up for grabs in the elections, while Scotland and Wales each had more than 1,000 seats at stake.

The elections decide who will be responsible for handling local issues such as planning, housing and rubbish collections – but wider national issues such as the surge in the cost of living have also come to the fore.

Results could also prove key to the future of the prime minister – and whether rumblings of backbench discontent escalate into a chorus of opposition triggering a no-confidence vote.

They will also shed light on whether Sir Keir has been able to make ground amid the pressures facing the PM as a result of partygate, the cost of living crisis and questions about the culture in Westminster.

In Northern Ireland, 90 assembly members are being elected – with tensions high as polls point to Sinn Fein overtaking the DUP as the largest party, suggesting Northern Ireland could have a nationalist first minister for the first time.

Mayoral votes also took place – in South Yorkshire, Croydon, Hackney, Lewisham, Newham, Tower Hamlets and Watford.

Voters in Bristol chose to scrap the directly elected mayor system in the city in a referendum.