The Labour leader is facing mounting pressure to distance himself from his former allies as he looks to consolidate his leadership credentials ahead of the 2020 election.
The latest poll shows him trailing rival Owen Smith by a wide margin, while he is at risk of losing support among Labour supporters in areas including the north and the Midlands, and among his own supporters in London.
In his bid for re-election, Mr Corbyn has been urged to set out his own agenda on issues such as Trident, immigration and foreign policy, with a focus on the working class.
“The key issue to the Labour Party in 2020 is not a party of the left but a party that represents the working and middle classes,” said Andrew Fisher, a professor of politics at Durham University.
While many unions have backed Mr Corbyn, some have been less enthusiastic about him and are more likely to back his challenger, Owen Smith, rather than the Labour leader.
Corbyn ally John McDonnell, a former shadow chancellor, has been pushing Mr Corbyn to stand down from the party after a number of senior figures in the party were implicated in the “Panama Papers” leaks, which exposed the details of their financial dealings with foreign governments.
But in a recent interview with the BBC, Mr McDonnell said he would not stand for a leadership contest against Mr Smith.
He said: “I have no intention of being leader of the Labour party.
We have to get back to the fundamentals.
We have to talk about the issues of our time, and we need to do that in a way that’s positive and not divisive.”
“We have got to make sure that we’re going to win the next election.
I believe we can win.”
Mr McDonnell has also called on the government to scrap the controversial Prevent counter-terrorism powers, which he said had “completely lost the public’s trust”.
The Labour leader has faced criticism for his links with his former political allies, including former deputy leader Harriet Harman and former shadow foreign secretary Hilary Benn.
Mr Corbyn is also under pressure to reveal whether he has been paid for appearances on BBC Radio 4’s Today programme or whether the appearance fee for one of his appearances has been reimbursed.
More than 400,000 people have signed a petition calling on the Labour leadership to withdraw Mr Corbyn’s nomination for the 2020 general election, with some claiming he is “unfit” to lead the party.