Jeremy Corbyn says he will not step down following Labour’s Copeland by-election loss to the Conservatives.
The Labour leader said the result 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.
The Conservatives seized the Cumbria seat for the first time in more than 80 years.
Their victory was the first by-election gain by a governing party since 1982.
‘Not a macho leader’
But there was happier news for Labour in the Stoke-on-Trent Central by-election, Gareth Snell held off the challenge of UKIP leader Paul Nuttall to regain the seat.
Mr Corbyn said while it was “a day of disappointment in Copeland” he would not be quitting as Labour leader. Asked if he would fall on his sword following the defeat, he said: “No. I was elected leader of this party – I’m proud to lead this party.”
Mr McDonnell said while he conceded there were “mixed views on Jeremy”, the result was not about individuals and the Labour leader was not considering his position. “He’s never said that,” he said.
“He’s a different type of leader. He is that sort of person who does listen, who is decent and honest and does bring people together.
“He’s not the sort of macho leader we’ve seen in the past, and that’s why we’ve had the disasters that we’ve had,” he said.
“Our party has got to rebuild itself from the grassroots in the communities like Copeland.”
Mr McDonnell said Mr Corbyn “wants to serve this community and he’ll do it well once he becomes prime minister … because he understands how people feel in places like Copeland”.
But he urged the party to unite, and said Mr Blair’s speech a week ago, in which he claimed the “debilitation of the Labour Party is the facilitator of Brexit” had not been helpful.
“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.
Pressed on whether he was blaming Mr Blair for the by-election defeat, Mr McDonnell said: “It’s not his fault. I’m just saying, advice: please don’t do that.
“And the same to Peter Mandelson – three days before a by-election he attacks the party. What I’m saying is the central principle of how you win elections is you have a united party, you do not divide the party.”
But John Woodcock, Labour MP for Barrow, the neighbouring constituency to Copeland, said the by-election loss showed the party was “in trouble”.
While he did not back another challenge to Mr Corbyn, he said Labour must provide more effective opposition.
Mr Woodcock said there were “always excuses” for parties after they lost by-elections and the party must be doing much better nationally.
Asked if Labour could win the next general election, he told Today the party was “actually on course to a historic and catastrophic defeat”.
That would have “very serious consequences for all of the communities that we represent and the causes that the Labour party stands for,” he said.
The MP said it would be “counter-productive” for him and other critics of Mr Corbyn to demand another leadership election when the outcome was likely to be another victory for Mr Corbyn.
“Jeremy Corbyn is going to remain leader of the Labour Party unless he decides that he thinks that it is right to go,” he said.