Labour MP Angela Smith has said the party's 'terrible' by-election defeat in Mosborough was down to traditional party supporters refusing to vote for Jeremy Corbyn.
The Penistone and Stocksbridge MP said people in Mosborough are 'turning their backs on our party' because they do not believe Corbyn is a credible candidate to be Prime Minister.
In an article for Labour List, Smith said Labour's 'really shocking' defeat to the Liberal Democrats was down to people's negative reaction to the party leader.
A by-election was held in Mosborough on Thursday following the death of Labour councillor Isobel Bowler earlier this year.
Labour party candidate Julie Grocutt lost to Liberal Democrat Gail Smith, who secured a 31 per cent swing to win the seat after the party came fourth behind Labour, UKIP and the Tories back in May.
The defeat comes just weeks after Corbyn held a huge rally in Sheffield city centre attended by thousands of people.
Smith said the reaction to Corbyn on the doorstep is very different to those seen at his rallies.
She said: "We had a brilliant candidate in Julie Grocutt, a former police officer and trade union rep.
"She’s a town councillor in Sheffield with a well-deserved reputation for community service. She’s a phenomenal campaigner too, putting petrol in her car to campaign across Sheffield and Barnsley for Labour.
"Her years of hard work meant Labour members came out to help her campaign. We knocked on more doors and delivered more leaflets than in most council by-elections I can remember.
"Until last night, we had all three councillors in the ward. And with a great candidate and a good campaign, we should have held the seat, so there’s no point pretending this was anything other than a crushing defeat. A terrible setback. And failing to listen hard to what the voters told us would be criminal.
"Anyone who knocked on doors in Mosborough will tell you very clearly why we lost. Traditional Labour voters refused to vote for Jeremy Corbyn. I knocked on door after door and heard the same message. Even yesterday, as we were knocking up to get people to the polls.
"'Sorry love,' a former steel worker who’d voted Labour all his life told me, 'I just can’t vote Labour with that man in charge'."
"On the doorstep I met people affected by benefit cuts, relying on food banks or struggling to find work. I saw how the Tories’ cuts are destroying crucial local services. But I also met people who have voted Labour through thick and thin but are turning their backs on our party because they just do not believe Jeremy will ever be a credible candidate for prime minister.
"Too many residents told me they thought he was weak. They think he is not capable of leading the Labour Party, let alone the country. They can’t imagine him on the doorstep of Number Ten welcoming an American President – let alone negotiating with Putin.
"Others told me he was out of touch on issues like welfare or immigration and that they wouldn’t trust him with the economy or the country’s defences.
"Residents in Mosborough told us the same message as voters across the country are telling the pollsters."
Smith added: "His supporters tell us that he’s won Parliamentary by-elections, but these were all in Labour seats.
"They point to his rallies, but cheers from your supporters clearly don’t translate into votes at the ballot box. Just three weeks ago he spoke to the converted in Barkers Pool Square in Sheffield and a fat lot of good that did. Perhaps he should have brought them out to knock on doors and listen to the public instead.
"They claim that he has motivated a huge number of people to campaign for Labour, and it’s true that 40 people were in Sheffield in a Momentum phone bank last night. Unfortunately, while we were knocking on doors and ringing residents to get them to vote Labour, they were ringing members asking them to vote for Jeremy.
"I know lots of members disagree with me about Jeremy. All I ask is that we stop talking to ourselves, come out campaigning and listen to people whose trust we need to win back.
"That’s the only way we can avoid a lot more terrible defeats like last night’s in Mosborough."
Her comments came as a Labour activist who campaigned in Mosborough said people in the ward 'absolutely despise Jeremy Corbyn'.
Writing on Reddit, the activist said: "To quote some of the campaigners who worked with me: Anyone who spent any time in Mosborough will know that the number one issue raised by Labour voters was Jeremy Corbyn.
"In our city plagued by inequality, Mosborough is as close to 'England average' as Sheffield gets.
"If this is the response in Mosborough, just think what it will be like in the rest of England."
The activist said that Julie Grocutt had 'ousted herself internally as anti-Corbyn, hence the Corbynites didn't vote for her or rally behind her'.
They added: "The people of Mosborough didn't know this - and absolutely despise Jeremy Corbyn, hence didn't rally behind her.
"Hence, we got stuck between a rock and a hard place on this one - all the Lib Dems had to do was circulate one anti-Corbyn leaflet and it was over before it had begun.
"I'm worried this may become our new reality, as we seem to be dropping further down in the polls...
"I, personally, am seriously worried about the future of the party, electorally speaking, if we're unable to keep safe seats like Mosborough due to internal squabbling and poor national leadership."