Hopes of a Labour revival under Sir Keir Starmer have suffered a blow after the Conservative Party comfortably won the Hartlepool by-election.

The Leave-supporting North East constituency went blue for the first time in its 47-year-old history, as Boris Johnson demolished another brick in Labour’s so-called “red wall”.

Voters in the town backed Tory candidate Jill Mortimer to be their next MP over Labour’s Dr Paul Williams – an avid Remainer and second-referendum campaigner during his time as MP for Stockton South from 2017-19 – in a rare by-election victory for a party in power for more than a decade.

The Conservative, who declared it a “truly historic result”, secured a 6,940 majority winning 15,529 votes to Dr Williams’ 8,589.

Ms Mortimer told supporters: “I’m going to work tirelessly for Hartlepool and I will not let you down, I will not fail you.”

The defeat was signalled by senior figures hours before the official announcement, with shadow transport secretary Jim McMahon telling Sky News shortly before 3am his party was “not close to winning this”.

The result will be a setback for Sir Keir, who took over as Opposition leader from Jeremy Corbyn four months after the party’s disastrous 2019 general election performance with the promise of turning it back into a winning force.

It is likely to mean questions about the strategy he has pursued as leader over the past year, with traditional Labour voters seemingly continuing to turn away from the party in the wake of Brexit.

Early results in council contests after the Super Thursday elections appeared to show voters deserting Labour, with the Tories seizing Redditch and Nuneaton & Bedworth councils in the Midlands, along with Harlow in Essex, while Sir Keir’s party saw heavy losses across North East local authorities.

A Labour source said Sir Keir would “take responsibility for these results” and for “fixing” the party’s electoral woes.

Prominent figures from the left wing of the party were quick to criticise the outcome and the approach taken.

Former shadow home secretary Diane Abbott tweeted: “Not possible to blame Jeremy Corbyn for this result. Labour won the seat twice under his leadership.

“Keir Starmer must think again about his strategy.”

Communities Secretary Robert Jenrick had sought to pile pressure on the Prime Minister’s rival before the declaration, telling Sky News that “if it is even close, I would say that is a really serious indictment of Keir Starmer”.

Shadow cabinet minister Thangam Debbonaire admitted the party’s new messaging was “not cutting through”.

Alex Norris, shadow public health minister, denied that the loss was Sir Keir’s responsibility and pointed to the coronavirus pandemic as a factor in the lack of progress made in the polls under his leadership.

“In the entire period Keir has been leader we’ve been in a global pandemic and he hasn’t been able to give a public appearance yet,” he told Sky News.

“So actually, I think he has done a great job in connecting the way he has, and we’ve got more to do.”

Hartlepool was held by Labour with a majority of 3,595 in 2019, even as other bricks in the red wall crumbled – in part due to the Brexit Party splitting the Tory vote.

Both Mr Johnson and Sir Keir made three visits during the campaign in a sign of the importance the by-election represented to their parties.

A Labour source said: “We’ve said all along the North East and the Midlands would be difficult.

“But the message from voters is clear and we have heard it – Labour has not yet changed nearly enough for voters to place their trust in us.

“We understand that. We are listening. And we will now redouble our efforts.

“People don’t want to hear excuses. Keir has said he will take responsibility for these results – and he will take responsibility for fixing it and changing the Labour Party for the better.”

Following the Hartlepool declaration, attention will turn to results elsewhere as ballots continue to be counted across England, Scotland
and Wales in the largest test of political opinion outside a general election.

Results from the Holyrood election – where the issue of Scottish independence was a main feature in the campaign – will come through later on Friday and Saturday.

Scottish National Party (SNP) leader Nicola Sturgeon’s push for a second independence referendum means the stakes are high in the contest.

The SNP is expected to emerge again as the largest party in the Scottish Parliament after the election, but it wants to win an overall majority of MSPs as it pushes for a second vote on splitting from the Union – something which polls suggest remains in the balance.

Mr Johnson has refused to countenance another poll, setting up the potential for constitutional fireworks over the coming years if Ms Sturgeon gets the outcome she desires.

Results of the elections – which also include the Welsh Parliament, police and crime commissioners and English local authorities and mayors – are expected to continue filtering through until Monday as counting will take longer than normal due to coronavirus restrictions.

In Wales, Mark Drakeford hopes to maintain Labour’s grip on the Senedd – but he may find himself forced to forge a new coalition to stay as First Minister.

That could mean talks with Plaid Cymru, whose leader Adam Price has committed to an independence referendum within five years if his party wins a majority.