The Conservatives do not deserve to be in power “for a moment longer”, Labour leader Sir Keir Starmer said in a fresh challenge to Rishi Sunak following his party’s local election defeats.

The Labour leader also said he was confident Sadiq Khan could win a third term as Labour mayor of London, amid suggestions the contest with Tory challenger Susan Hall could be closer than expected.

Both the Prime Minister and Sir Keir are braced for the results of the key mayoral elections in London and the West Midlands, which is also expected to be a narrow contest for Tory incumbent Andy Street.

As Friday’s result declarations closed, the Conservatives had suffered a net loss of 371 seats, and lost control of 10 councils.

Overall, Labour won control of eight councils as it saw a net gain of 204 seats, and saw victory in three inaugural mayoral races in the East Midlands, the North East, and in York and North Yorkshire, a region which includes Rishi Sunak’s Richmond constituency.

Speaking in Mansfield alongside the new Labour mayor of the East Midlands, Claire Ward, Labour leader Sir Keir said: “I think the message here is very, very clear, and I think across the East Midlands there has been a sending of that message to the Government, which is we are fed up with your division, with your chaos, with your failure.

“Fourteen years, and I am sorry, I don’t care which political party you support, if you leave your country in a worse state then when you found it 14 years later you do not deserve to be in Government for a moment longer.”

Several more mayoral polls will be declared on Saturday, with London and the West Midlands viewed as the most significant.

As results declarations began to come in, Labour held on to mayoralties in Liverpool and South Yorkshire.

Sir Keir brushed off concerns about Mr Khan’s fortunes in the London ballot, telling reporters: “Sadiq Khan was absolutely the right candidate. He has got two terms of delivery behind him and I am confident that he has got another term of delivery in front of him.”

Early constituency results proved promising for Mr Khan, with the Labour mayor winning 83,792 votes in Greenwich and Lewisham, followed by Conservative Susan Hall on 36,822 and Zoe Garbett of the Greens third with 11,209.

In Merton and Wandsworth Mr Khan received 84,725 and Ms Hall 50,976.

Further Tory losses in Saturday’s results could be fodder to Tory rebels set on ousting Mr Sunak before the general election, though the Conservative’s win in the Tees Valley mayoral election on Friday appears to have quelled the revolt.

Lord Ben Houchen retained the mayoralty, amid denials he had sought to distance himself from the Conservative party during his campaign.

In a defiant message closing out the first day of results, Mr Sunak suggested there was still hope for his party despite already suffering bruising defeats in the final test of voters before a general election.

He wrote in the Telegraph newspaper: “Thursday’s results showed that voters are frustrated and wondering why they should vote. The fact Labour is not winning in places that they admit themselves they need for a majority, shows that Keir Starmer’s lack of plan and vision is hurting them.

“We Conservatives have everything to fight for – and we will because we are fighting for our values and our country’s future”.

Mr Sunak pointed to his party’s recent commitment to hike defence spending, and measures to grasp migration as clear dividing lines with Labour.

Sir Keir’s takeaway ahead of the general election was to “turn the page on decline”, as he drew attention to Labour’s plans to “pick up the NHS”, make sure the streets are safe, build affordable homes, and provide secure jobs.

The party took a Tory scalp by winning the Blackpool South by-election, but lost seats to independents and George Galloway’s Workers Party of Britain in a smattering of councils, apparently over its stance on Gaza.

In Friday’s results the Liberal Democrats gained 92 seats and the Greens 58.

The Liberal Democrats’ most significant victory was winning control of Dorset council from the Conservatives, where it now has 42 of the 82 seats after gaining 15.

The Greens fell narrowly short of taking overall control of Bristol, one of their top targets, despite gaining 10 seats.