More than 125,000 Labour members not entitled to vote in the party’s leadership contest could now be allowed to take part after a court ruling.
Five members have won a High Court battle with Labour, which had banned anyone who joined after 12 January from voting unless they paid an extra £25.
The party has been granted permission to appeal against the ruling, which is thought likely to benefit leader Jeremy Corbyn over challenger Owen Smith.
The appeal could be heard on Thursday.
The court’s decision could add anywhere between 126,592 and 150,000 people to the list of those eligible to vote in the contest – according to different estimates.
Mr Smith is calling for the leadership contest – due to end on 24 September – to be extended “so that all members have the opportunity to engage with Jeremy and me before making their choice”.