Jeremy Corbyn has come under intense pressure to take some personal responsibility for Labour’s historic by-election defeat in Copeland from senior party figures, including trade union leaders and even members of his own shadow cabinet.
The Labour leader was urged not to “pass the buck” or sugarcoat the result after Theresa May’s Conservatives secured the first by-election gain by a government since 1982, in a Cumbrian seat that had been held by his party since 1935.
As some claimed the result placed Labour on track for electoral meltdown, the general secretary of a trade union that has backed Corbyn in two leadership elections issued a stark warning.
Unison’s Dave Prentis described the Copeland result as “disastrous”. “No one objective could argue last night’s by-election results were good for Labour,” he said.
The Unison leader welcomed Labour holding off the Ukip leader, Paul Nuttall, in a second byelection in Stoke, although he said even that result should never have been in doubt.
“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,” he said.
Keir Starmer, the shadow Brexit secretary, argued that the result was not simply about Labour’s battle to come to terms with an EU referendum result that had divided its coalition of voters.
He told the Guardian that the outcome was more “fundamental” than the question of Brexit, adding: “It was a very bad result... I’m not sure we are acknowledging how bad a result it was.”
The prime minister described the result as “astounding” after her party secured a 6.7% swing from Labour, handing Trudy Harrison the seat with 13,748 votes, ahead of Labour’s Gillian Troughton on 11,601.
The result overshadowed Labour’s victory in Stoke-on-Trent Central, where the party’s Gareth Snell defeated Nuttall by 7,853 votes to 5,233, in a constituency that some had described as one of Britain’s Brexit capitals.
Corbyn used broadcast interviews and a speech focused on Labour’s Brexit challenge, making it clear that he did not believe his leadership contributed to the defeat in Copeland and said he would not be stepping down.
The Labour leader admitted he was disappointed by the result in the Cumbrian constituency but said it was important to highlight the victory in Stoke. “You shouldn’t underestimate the defeat for Ukip in a city they began to call their own.
It is a very significant turning point in British politics,” Corbyn said, claiming that the media had assumed Labour would be defeated in Stoke.
Asked by a journalist if he had looked in the mirror to ask whether Labour’s problems were his fault, Corbyn responded with a curt “no”.  The shadow chancellor, John McDonnell, hit out at disunity within Labour, blaming both sitting MPs and Tony Blair and Lord Mandelson, who criticised the party’s approach to Brexit.
“We cannot have a circumstance again, where a week before the by-election a former leader of our party attacks the party itself,” he said.
Ian Lavery, the party’s joint elections co-ordinator, told the Guardian that his time campaigning in Copeland had convinced him that the challenge was about people’s fears for their jobs and not Labour’s leadership. “Honestly, Jeremy Corbyn did not come up when I was knocking on doors,” he said.
Lavery joined other shadow cabinet members, such as Richard Burgon, in describing the Cumbrian seat as “marginal” despite it always being held by Labour previously.
Another senior figure in the party suggested that unfair treatment of Corbyn in the media, including the BBC’s decision to field Mandelson days before the election, and bad weather as a result of Storm Doris had contributed to the defeat.
Despite some senior sources hitting out at fractious MPs who forced Corbyn into a second leadership battle last year, critical backbenchers were largely quiet on Friday.
Some said there was a “vow of silence” in order to prevent disunity in the immediate aftermath being blamed for any of Labour’s difficulties in the future, although sources close to the leadership claimed “unnamed MPs” seemed happy to attack the leader.
One MP, David Winnick, did criticise the leader openly, while a number of senior figures in the wider Labour movement also waded into the debate.
John Hannett, the general secretary of Usdaw, the shop workers’ union which has not supported Corbyn in his bids for the leadership, called the the result a “wake-up call” and warned the Labour party not to “pass the buck”.
“We can’t dismiss these by-elections or blame other people — whether previous politicians or the media,” he told the Guardian. “All of that is a distraction from why isn’t the current Labour party connecting with voters.”
He said there needed to be an “urgent debate” from the leadership team down about how to turn Labour into at least a “credible opposition” and then a government-in-waiting.
The concerns were based on fears of Labour being wiped out from parts of the country if May decided to trigger an early general election.
A projection from Electoral Calculus based on recent polls suggests a Conservative majority of 80 would occur with 41% of the vote going to the Tories and 27% to Labour.