Corbyn, who was elected leader less than a year ago, has been challenged for the role by lawmaker Owen Smith.
Members of Britain's opposition Labour party who had been excluded from voting in its leadership contest have won a court battle to have their say on whether Jeremy Corbyn should stay in the job following a challenge from one of his lawmakers.
The party has been in turmoil since Britain's June 23 vote to leave the European Union, with critics of veteran left-winger Corbyn saying he did not do enough to support the campaign to stay in the bloc and would not be able to win a general election.
Corbyn, who was elected leader less than a year ago, has been challenged for the role by lawmaker Owen Smith. While Smith has the backing of a majority of the party's lawmakers, Corbyn retains strong support among grassroots members.
Labour's national executive committee ruled last month that members who had joined the party since Jan. 12 would not be eligible to vote, a decision which local media reported would exclude as many as 130,000 new members, unless they paid a further 25 pounds ($32) to register as a party supporter.
Five members challenged that decision and on Monday a High Court judge ruled that they had joined the party on the basis they would be able to vote in any leadership contest.
"For the party to refuse to allow the claimants to vote in the current leadership election, because they have not been members since 12 January 2016, would be unlawful as in breach of contract," the judge said, according to the Press Association.
Labour was given permission to appeal the decision.
Corbyn is the bookmakers' favourite to win when the result is declared on Sept. 24. It is not clear what proportion of new members had signed up in order to vote for him again.