Jeremy Corbyn vows to continue despite humiliating Copeland by-election defeat

The Labour leader said the result was "very disappointing" but made clear he was determined to carry on.

"I was elected to lead this party. I am proud to lead this party," he told reporters. "We will continue our campaigning work on the NHS, on social care, on housing."

One leading trade union figure warned Mr Corbyn he had to "turn things around" and show he could deliver a Labour government.

Following a tumultuous night, a jubliant Theresa May travelled north to Copeland to hail an "astounding" victory for Tory candidate Trudy Harrison.

Her triumph was the first gain for a governing party in a parliamentary by-election since 1982.

Ms Harrison polled 13,748 votes to 11,601 for Labour's Gillian Troughton, increasing the Conservative vote share by more than 8% as Labour's dropped by nearly 5%.

The Prime Minister told cheering supporters: "What we have seen from this victory is that this truly is a Government that is working for everyone and for every part of the country."

There was some consolation for Labour in Stoke-on-Trent Central, where it saw off a concerted challenge from Ukip leader Paul Nuttall - albeit with a reduced majority.

But there was despair among MPs at the defeat in Copeland, with John Woodcock, MP for neighbouring Barrow-in-Furness, warning the party was heading for disaster at the general election.

"We are on course to a historic and catastrophic defeat and that will have very serious consequences for all of the communities that we represent," he told the BBC Radio 4 Today programme.

Senior Labour backbencher David Winnick said Mr Corbyn was an "obstacle" to victory and should consider his position.

"The party is faced with the problem of a leader who is simply not acceptable to a large number of people who would normally vote Labour," he told the Press Association.

"It is now entirely up to Jeremy and those close to him to decide what is best in the interests not simply of the party but the people we are in politics to represent."

Dave Prentis, general secretary of the Unison trade union, said that while the blame for a "disastrous" defeat did not lie solely with Mr Corbyn, he had to take responsibility for what happened next.

"Nurses, teaching assistants, care workers and ordinary people everywhere need a Labour government. Jeremy has to show he understands how to turn things around and deliver just that," he said.

Despite the despondency on the Labour benches, there was little mood for a fresh leadership challenge, with MPs fearing it would lead to a repeat of last year's crushing victory for Mr Corbyn.

Labour campaigns chairman Ian Lavery - a leadership loyalist - insisted the by-election was not a ballot on Mr Corbyn's leadership.

"Jeremy Corbyn is one of the most popular politicians in the country at this moment," told BBC2's Daily Politics.

Shadow chancellor John McDonnell, one of Mr Corbyn's closest allies, hit out at Tony Blair and Lord Mandelson for high-profile interventions in the days before the by-elections.

"We can't have a circumstance again where a week before the by-election a former leader of our party attacks the party itself," he told the Today programme.

Ukip was also forced on to the defensive after Mr Nuttall's gamble of standing in Stoke Central failed to pay off, despite overwhelming support for Brexit in the city in last year's EU referendum.

After Gareth Snell held the seat for Labour with 7,853 votes to Mr Nuttall's 5,233, Ukip chairman Paul Oakden acknowledged it could be years before the party won a seat in Westminster.

"It took us 23-odd years to win a referendum to get Britain out of the European Union. It may take that long for us to get a seat in Westminster via a by-election," he told Today.

Mr Corbyn went to Stoke to congratulate Mr Snell on his victory, telling cheering supporters that Labour was working for "an economy that is based on investment, based on good jobs, based on growth, based on opportunities for everybody in our society".

"Ukip can't offer that, the Tories can't offer that. We can, we will, and we will win," said the Labour leader, who left without taking questions from reporters.

Addressing several media crews near the Potteries Museum and Art Gallery, Mr Corbyn criticised journalists for interrupting each other as they shouted questions about the defeat in Copeland.

Immediately before he left the public area outside the museum, he asked reporters: "Why can't you learn to be polite to each other?"

Labour's shadow leader of the Lords, Baroness Smith, described the Copeland defeat as "devastating" and said Mr Corbyn should "think long and hard" about his response.

Lady Smith told the Huffington Post UK: "We mustn't bury our head in the sand, this is a very bad election result for us.

"I think Jeremy will be very disappointed at the election result ... I can't believe for one moment he draws any comfort from that result and he will be clearly be thinking long and hard about it."

Lady Smith suggested that Mr Corbyn's long-standing personal objections to nuclear power may have harmed Labour in the Cumbria seat, which is home to the Sellafield reprocessing plant.

"The leader has to reflect official Labour party policy," she said "The Labour Party has always been a broad coalition, and on nuclear there's always been differently held views. Yet the leader has to reflect the views of the party as a whole."

The leader of the shop-workers' trade union Usdaw, John Hannett, said that the by-election results "raise questions about Labour's electability and the vision it offers to the people of this country".

Mr Hannett said: "The electorate clearly have doubts about Labour's message and direction of travel. All sections of the party, from the Leader to elected office holders and the members, need to listen to those doubts and learn from them.

"Labour needs a clear, credible message that people can believe in and Jeremy Corbyn needs to take responsibility for delivering that sooner rather than later."