That's it for the by-election reaction page. Our main story is here and will continue to be updated with the latest developments.
- Conservatives gain Copeland from Labour in by-election
- Labour win Stoke Central by-election, fighting off UKIP challenge
- Theresa May hails new MP Trudy Harrison's "astounding victory"
- Jeremy Corbyn "disappointment" over Copeland, but celebrates Stoke
The Guardian's North of England correspondent Josh Halliday has spoken to voters in Copeland about why they think Labour lost its eight-decade hold on the constituency.
"Many commentators felt the Labour leader’s perceived anti-nuclear stance would prove toxic in Copeland, where more than 10,000 jobs rely on the industry, but it appears the feeling runs far deeper than that," he writes.
The Socialist Worker newspaper has welcomed Labour's victory in Stoke-on-Trent Central but said the defeat in Copeland was "disastrous".
"The right wing in Labour have two explanations for the party’s weak showing - and both of them are wrong," writes Nick Clark.
"There is a long-tern process of disillusionment with a Labour Party that has not acted in working class people's interests."
UKIP should have been tougher on immigration when campaigning in the Stoke-on-Trent Central by-election, former leader Nigel Farage says.
Mr Farage told the BBC the party needed to learn lessons after his successor Paul Nuttall failed to unseat Labour.
He had warned the contest was "fundamental" to the party's future prospects.
"There is a debate in UKIP as to how strong we should be on the immigration issue. I personally think we should own it. So we will have to look at that and think: Were we really tough enough, were we clear enough with the electorate? It has got to be looked at."
The World at One
BBC Radio 4
Neil Hamilton leads the UKIP group in the National Assembly in Wales. He told Shaun Ley that "in two or three years time, UKIP's opportunity will come back as regards the Tories".
BBC News Channel
Labour's only Scottish MP Ian Murray says the party's MPs and MSPs are "right behind" leader Jeremy Corbyn.
Mr Murray told a fringe meeting at Scottish Labour's conference in Perth: "Since Jeremy was re-elected there has been no disloyalty to Jeremy at all.
"There has been a bit of an argument about Europe but, you know, people would expect us to have that.
"There is that need for us to get behind (him) as one united house, as you put it, but I will say this... if we fail to listen to the public we deserve everything we get.
"That goes across every single political party, it goes across every trade union, every business.
"You get what you deserve if you don't listen to your customers or your voters, and what people are telling us on the doorsteps, whether we like hearing it or not, is they don't think that the Labour Party has a pathway to power at Westminster and therefore they will take their votes elsewhere."
Labour MP John Woodcock, a fierce critic of Jeremy Corbyn, appeared on the Daily Politics earlier.
In a footnote to all the by-election buzz, in the latest council by-elections the Tories suffered setbacks while Labour and the Liberal Democrats saw gains.
The Lib Dems took a seat from the Tories in a contest at South Hams District Council and gained another at Kettering Borough Council.
Earlier this week, Labour gained a seat from the Tories at Basingstoke & Deane on a large 20.8% swing.
Mr Corbyn said Labour campaigners had overcome those who had written the party off and predicted UKIP would win in Stoke.
He said: "I'll tell you what happened yesterday: people came out, worked, knocked on doors and delivered a message.
"It's a message about the economy, it's a message about jobs, it's a message about this country.
"But above all it was a message that hope triumphs over fear."
The Labour leader is in Stoke to congratulate his newest MP, Gareth Snell.
Mr Snell told supporters: "What we have shown (is that) when we are united and committed and determined we will win elections, and that is exactly what we are going to do."
Unison general secretary Dave Prentis says no-one could argue that the by-election results were good for Labour.
While it was pleasing to see Ukip put in its place, Stoke should never have been in doubt and the result in Copeland was disastrous.
"The blame for these results does not lie solely with Jeremy Corbyn, but he must take responsibility for what happens 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."
BBC News Channel
The former UKIP leader Diane James says the "whole Labour machine mobilised to defeat and discredit" Paul Nuttall.
Ms James - now an independent MEP - says Mr Nuttall should remain as UKIP leader.
The Financial Times' leader writer and digital comment editor, Sebastian Payne, says the by-election results show that traditional political alliances have "not been entirely reset" since the Brexit vote fallout.
BBC News Channel
The MEP and former UKIP leader said Mr Nuttall had gone through a "pretty bruising experience" in the face of an "onslaught" from Labour on the campaign trail.
She added: "He took a very high risk strategy in terms of standing.
"I think that's one aspect he will probably rue going forward, but I don't see and I would not want to see him stand down.
"He is going to be a very good leader and UKIP's got a future."
Jeremy Corbyn said the Copeland by-election loss was disappointing, but he had been elected twice and was "proud" to continue.
Shadow Chancellor John McDonnell claimed there were "mixed views" about Mr Corbyn's leadership but the defeat in Cumbria wasn't "about individuals".
But MP John Woodcock said the party was facing an "historic and catastrophic" defeat at the next general election.
Read more here .
The Labour leader said his party's message was "not enough" to win the Copeland by-election, but he hailed Labour's victory in Stoke-on-Trent Central.
In a speech in London, the Labour leader said both constituencies had been "let down by the political establishment".
Speaking after Mrs May, a jubilant Trudy Harrison thanked the people of Copeland for putting their faith in her and helping her to a "historic" win.
The new Tory MP told them: "I am really looking forward to getting on with the job.
"I am very much looking forward to going down to London on Monday and making sure that we deliver on the plan that I have been pledging for the last four weeks."
Mrs May hails Trudy Harrison as a "fantastic candidate".
Trudy isn't just somebody who talks about things, she actually rolls up her sleeves and gets things done.
"The people of Copeland are going to see that they have elected a member of Parliament who is going to listen to their concerns, who is going to raise her voice.
"She will have the ear of government, but she will ensure that she delivers for the people of Copeland."
Mrs May tells Tory supporters: "This is truly a wonderful victory for the Conservative Party but also for the people of Copeland.
What I think we've seen from this victory is that this truly is a government that is working for everyone and for every part of the country."
Prime Minister Theresa May says she is "absolutely delighted" at the by-election victory in Copeland.
This is an astounding victory for the Conservative Party but also for the people of Copeland."
BBC Radio 5 live
Lifelong Labour voter Pauline Greers believes Labour should "think about who's at the helm" after losing the Copeland by-election to the Conservatives.
She told 5 live Breakfast she had this message for shadow chancellor John McDonnell: “I’ve been a staunch Labour voter all my life like my dad before me. I was unsure whether they would get in but I’m really disappointed.
“I think [they] need to think about who’s at the helm and change things.”
The Conservative MP and former health minister, Dr Dan Poulter, says the result in Copeland is a strong endorsement of Theresa May as prime minister.
He said: "Of course in any by-election there are factors in place. Some of those are local factors. Some of those are national factors.
"But it's always expected that the main opposition does well in national by-elections.
"That wasn't the case and what this by-election has shown, I believe, and certainly from what I pick up in my own constituency and elsewhere in the country is that there is a very strong belief in Theresa May as our prime minister - and that's something that was borne out, I believe, in this election result today".
Jamie Reed, whose resignation triggered the Copeland by-election, has tweeted his verdict on the loss of the seat.
The UKIP leader has tweeted thanks following his unsuccessful campaign in Stoke-on-Trent Central.