Former Labour deputy leader Tom Watson has said he stood down as an MP last month due to the “brutality and hostility” within his own party.
Speaking to the Guardian, he said criticism from factions and on social media had become a “heavy load”.
The former West Bromwich East MP revealed that Labour Party officials had even concealed a death threat towards him.
“The point is that the brutality and hostility is real and it’s day to day,” he told the Guardian’s Weekend magazine.
“So I just thought: now’s the time to take a leap, do something different. You’ve had a good innings. You’ve done good stuff. Go now.”
The 52-year-old praised Jeremy Corbyn personally but was critical of his leadership.
Watson admitted voting for rival Owen Smith during the party’s 2016 leadership election.
Corbyn retained his position with 61 per cent of the vote among the party’s membership, despite having lost a vote of no confidence by 172 to 40 Labour MPs following the resignation of dozens of shadow cabinet ministers.
“I thought, as soon as the leader loses the confidence of the parliamentary party it’s almost impossible to see how you can form a government,” Watson said.
“I thought Jeremy should have resigned, and he nearly did.”
The party is now seeking a new leader after Corbyn said he would step down following Labour’s worst election defeat in 85 years.
The Conservatives won an 80-seat majority after claiming a number of traditional Labour strongholds across the Midlands and north of England, including Watson’s former constituency, West Bromwich East, which the Tories won for the first time with a majority of 1,593.
Watson criticised Labour’s election strategy for lacking a key message.
“There were announcements everywhere, but none of them got through because there were so many,” he said.
“You knew what Boris Johnson’s was: get Brexit done. What was the Labour strapline?”
Watson is now retraining as a gym instructor and has lost eight stone in weight.
Greater Manchester mayor Andy Burnham accepted Watson’s description of the situation and said the party “cannot carry on as we are”.
Speaking to BBC, Burnham said: “The tone of public discourse, generally but also internally, has become poisonous at times and I think Tom was very much bearing the brunt of that.”
The Labour MP, who came second to Corbyn in the 2015 leadership contest, said whoever becomes the next Labour leader must make the party “a broad church where we respect each other… as soon as possible.”