Labour voters have overturned decades of political tradition and defected to the Conservatives across its industrial heartlands, transforming the electoral map and ushering Boris Johnson towards a significant Commons majority.

In results that surpassed even Johnson’s wildest expectations, the Conservatives unseated Labour for the first time in decades in solid red seats from Wrexham in north Wales to Blyth Valley in Northumberland.

The shock of the exit poll, which predicted Labour’s worst general election result since the 1930s, gave way to dismay and anger as unseated Labour MPs blamed Jeremy Corbyn’s leadership for the party’s dismal showing.

At Spennymoor leisure centre, outside Durham, dejected Labour activists looked on as votes piled up for the Conservative candidates in Bishop Auckland and Sedgefield, mining communities where the closure of the pits cast a long shadow over the area’s politics.

Helen Goodman, the defeated Labour MP for Bishop Auckland, said Corbyn had proved toxic on the doorstep and called for him to resign. “It’s been clear now for the last two years that Bishop Auckland is a marginal seat and the road to No 10 goes through Bishop Auckland,” she said.

Facebook Twitter Pinterest Conservative supporters celebrate victory for their candidate for Bishop Auckland, Dehenna Davison, and their Sedgefield candidate, Paul Howell, at the vote count in Spennymoor, County Durham. Photograph: Richard Saker/The Observer

“The Labour party cannot win if it doesn’t have a leader who commands the confidence and trust in the British public. Until we do have such a leader we’re not going to win. As long as we don’t, we’re letting down the very people we were set up to support.”

Speaking to a huddle of journalists, Goodman said people “didn’t feel they could trust him, they didn’t understand him” and that MPs had a big problem presenting Corbyn to the sizable local community of army veterans. “There are 1 million veterans in this country so that’s a huge problem,” she said.

Caroline Flint, the former Labour frontbencher, became one of the most high-profile casualties of the night when voters in Don Valley, South Yorkshire, elected the area’s first Tory MP since 1922.

The first sign of a likely Tory landslide came shortly after 11.30pm when the former mining community of Blyth Valley unseated the veteran Labour MP Ronnie Campbell, electing a Conservative for the first time in its 69-year history.

Campbell, a former miner, had his majority cut from nearly 17,000 to 8,000 over the past two decades and saw a 10% swing in his vote to the Conservatives on Thursday. The Teesside constituencies of Darlington, Redcar and Stockton South all fell to the Conservatives as Labour’s so-called “red wall” crumbled down the north-east coast.

Labour also lost its grip on Sedgefield, the County Durham seat held for 24 years by Tony Blair, and neighbouring Bishop Auckland, which elected a Tory MP for the first time in its 134-year history as Brexit and Jeremy Corbyn proved the decisive issues for many in the north-east.

Phil Wilson, who took over from Blair as MP for Sedgefield in 2007, conceded defeat before his result had even been declared. His majority of 6,000 collapsed to a 4,500-vote majority for the Conservatives, in the party’s first win in the seat since 1931.

“I genuinely believe that the Corbyn leadership is the issue in this election and to say that it isn’t is delusional,” Wilson said. “Brexit is an issue, but for every one person who raised Brexit on the doorstep with me, five people raised the leadership of the Labour party.”

Wilson, whose pro-remain position was at odds with most of his constituents, said he did not regret standing up for what he believed in and said Labour had angered voters by “facing two ways” on Brexit.

“The Labour party’s got to go back to those core beliefs and the values of the Labour party. If you talk about them with confidence people will believe you on other issues, such as Brexit. You can’t win the argument on Brexit if you’re facing two ways,” he said.

“What I feel strongly about is the fact we let down Labour voters and that we’ve let down our communities and that we’ve lost four elections in a row,” he said, arriving at the county at Spennymoor leisure centre in the early hours of Friday.

“The last time we lost four elections in a row it took us 18 years. We’ve done that in nine years now. It’s going to be hard work re-establishing the bond between the Labour party and its voters. It’s more in anger than in sorrow because the people we’re representing have got another five years of a Tory government, which isn’t going to do very much for them.”

The Conservatives also gained the Cumbrian constituency of Workington, which had been Labour since the 1970s and whose “Workington man” stereotype of a working-class, rugby-watching voter became a key electoral target for the Tories.