Labour leader Corbyn admits failing to get through to voters in Cumbria
Labour leader Jeremy Corbyn has admitted his party failed to get its message through after losing the Copeland by-election.
Mr Corbyn also claimed the constituency, which has seen the Conservative Party's Trudy Harrison named as its next MP, had been "let down" by the political establishment.
Mrs Harrison was announced the victor following the count at Whitehaven Sports Centre after the polls closed at 10pm.
But Mr Corbyn, commenting on both this by election and one in Stoke, which his party held, said: "Labour's victory in Stoke is a decisive rejection of Ukip's politics of division and dishonesty.
"But our message was not enough to win through in Copeland.
"In both campaigns, Labour listened to thousands of voters on the doorstep.
"Both constituencies, like so many in Britain, have been let down by the political establishment.
"To win power to rebuild and transform Britain, Labour will go further to reconnect with voters and break with the failed political consensus."
Shadow chancellor John McDonnell has issued a plea for Labour unity, as one of the party's MPs branded its loss in the Copeland by-election a "disaster" which showed it was on track for a "catastrophic" general election defeat under Jeremy Corbyn's leadership.
The Conservatives dealt Mr Corbyn's party a humiliating blow by snatching the Cumbrian seat, in an area which had been represented by Labour MPs since 1935.
Labour took some solace from holding on to Stoke-on-Trent Central, where its new MP, Gareth Snell, had faced a concerted challenge from Ukip leader Paul Nuttall.
Victory for Mrs Harrison in Copeland was the first time a governing party had gained a seat in a parliamentary by-election since 1982, and represents a historic achievement for a party which has been in office for seven years of unrelenting austerity.
Mr McDonnell told BBC1's Breakfast he was "really disappointed" by the Copeland result, but insisted it was not a judgment on Mr Corbyn's leadership.
And he said voters in Stoke had done the nation a service by rejecting the "politics of dishonesty and division" represented by Ukip.
"This isn't about Jeremy Corbyn," said the shadow chancellor.
"This is about the position of the Labour Party for the future. We are in a difficult period over these last 20 months because of these leadership challenges and the divisions that have been sown within our party.
"The vast majority of our members want us now to unite and to campaign and hold the Government to account, and that's what we will do.
"These by-elections were difficult ones. We knew that.
"We've lost Copeland and we will learn lessons from that, but we've won Stoke and we've defeated something which was really dangerous for politics in this country.
"We've turned back the politics of dishonesty and division. The people of Stoke, by supporting Labour, have done us all a service in that."
Mr McDonnell said the Copeland constituency - whose last Tory MP was born in 1879 - represented a "unique" challenge for Labour because of the importance of the nuclear industry to its local workforce.
And he blamed "disinformation and misinformation" by Conservatives about Mr Corbyn's stance on the nuclear issue for undermining voters' support for Labour.
But Barrow MP and long-time Corbyn critic John Woodcock told the BBC Radio 4 Today programme: " There are always excuses you can make.
"But we are in trouble as a party. This is a time when the country really needs an effective opposition and they need an alternative to the very damaging approach which the Conservative Government is taking on the issue of leaving the European Union.
"We are not providing that at the moment and we have to do better."
Mr Woodcock, whose Barrow seat borders Copeland, accepted that Mr Corbyn's grassroots support meant he would r emain leader "unless he decides that he thinks it is right to go", but he added: " Certainly the position we are in at the moment, we are not on course for victory.
"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."
Ms Harrison polled 13,748 votes to 11,601 for Gillian Troughton, increasing the Conservative vote share by more than 8 per as Labour's dropped by nearly 5 per cent.