Shadow chancellor John McDonnell has rejected the idea that allies of Jeremy Corbyn support a High Court ruling that new party members should be allowed to vote in Labour's leadership election only because it could benefit the incumbent.
A judge ruled on Monday in favour of five supporters who accused Labour's National Executive Committee (NEC) of unlawfully "freezing" them out of the contest despite them having "paid their dues".
But party officials intend to mount a legal challenge in order to "defend the NEC's right" to uphold Labour's rules, with an appeal hearing expected to take place on Thursday.
The ruling has been viewed by many as a major boost for Mr Corbyn and it came on the same day that a slate of left-leaning candidates was elected on to the NEC – a development which could potentially help strengthen the Labour leader's grip on the party.
There has been speculation that the majority of new party members are likely to have joined in order to back Mr Corbyn as he seeks to fend off challenger Owen Smith.
And bookmakers seemed to agree, immediately moving to slash the odds of Mr Corbyn winning the contest in the wake of the court's decision.
Mr Corbyn's allies urged the party not to appeal against the ruling, stating that members' money should not be used to try to stop them from voting.
Mr McDonnell, chairman of Mr Corbyn's leadership campaign, said when people joined they were told "very clearly" they would be able to vote in the leadership contest and "to deny them that democratic right flies against all the traditions of our party".
He insisted his support for the ruling was not because it could improve Mr Corbyn's chances of victory.
He told Channel 4 News: "It's not a matter of whether it suits me or not because we don't know which way these members are going to vote – no-one knows that."
Mr Corbyn told BBC Newsnight that the court judgment seemed "very clear" that all party members should be allowed to vote.
"Surely that has to be the right decision," he said.
Meanwhile, Mr Smith has stressed "of course it's possible" that he could still win the contest, but he called for the timetable of the election to be changed.
Mr McDonnell had earlier claimed the decision to appeal had been taken by a "small clique" who opposed the Labour leader.
There has also been speculation that general secretary Iain McNicol could face being ousted if the party loses its appeal as divisions within the party deepen still further.
A senior Labour source said: "If Labour loses the appeal, the position of Iain McNicol becomes untenable."
The results of elections for seats on the NEC were also announced on Monday.
Six spaces for representatives from constituency Labour parties were filled with all six winners deemed to be on the left of the party.
Comedian Eddie Izzard failed to secure a seat.