That's it for the by-election reaction page. Our main story is here and will continue to be updated with the latest developments.
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
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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.Quote Message: "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.
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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."