The report by the Fabian Society follows a warning from Jeremy Corbyn’s most powerful union backer that the Labour leader may have to resign if the party’s poll ratings do not improve by the next election.
Len McCluskey, who is running for re-election as the general secretary of the Unite union, said Mr Corbyn and his deputy John McDonnell would have to consider their positions if Labour continued to perform poorly in the polls.
“Let’s suppose we are not having a snap election,” he said in an interview yesterday. “It buys into this question of what happens if we get to 2019 and opinion polls are still awful.
“The truth is everybody would examine that situation, including Jeremy Corbyn and John McDonnell.”
Mr McCluskey added: “These two are not egomaniacs, they are not desperate to cling on to power for power’s sake.” He later clarified that the Labour leader has his “full support”.
Labour trails the Conservatives by 15% in the latest opinion polls, despite signs the Tories are beginning to lose ground on after a peak in support following Theresa May’s appointment as Prime Minister.
The figures have prompted the intervention from the Fabian Society, which is traditionally associated with the New Labour movement led by Tony Blair.
Its analysis of polling and election data suggests that Labour is likely to win between 140 and 200 seats in cities and former industrial areas on as little as 20% of the vote, losing ground on the 231 constituencies it currently holds.
Fabian Society general secretary Andrew Harrop said: “As things stand Labour is on track to win fewer than 200 seats, whether the next election comes this year or in 2020.
“Even if Labour recovers it has almost no chance of securing a majority in a general election, because it needs over three million more votes than the Conservatives to win. Labour’s aim for now should be to move forwards not back and win enough MPs to be able to form a governing partnership with other parties.”
Allies of Jeremy Corbyn have previously called for a “progressive alliance” with the Greens and the SNP in comments that have been dismissed by Scottish Labour.
However, the prospects for a pact could grow distant as Mr Corbyn stakes out a tough stance on immigration to stave off the threat from Ukip. In his interview with the Daily Mirror, Mr McCluskey, who faces a challenge to his post as Unite general secretary from rival Gerard Coyne, warned that Labour needed to sort out its position on immigration and “get its narrative right on free movement”.
“We need to expose what Ukip stand for; not just anti-foreign but anti-workers’ rights, their hidden agenda on the NHS and welfare state,” he said. “But it will only work if ordinary people believe Labour is listening to their concerns and has solutions.”