Donor Michael Foster has lost his legal bid to overturn the British Labour Party's decision to guarantee Jeremy Corbyn a place on the leadership ballot.
Mr Foster brought the case against the party's general secretary, Iain McNicol, who was sued in a representative capacity, and Mr Corbyn.
He claimed that the Labour Party's rules were "misapplied" when its national executive committee voted by a majority of 18 to 14 that Mr Corbyn should automatically go on the ballot paper without needing to obtain the backing of 20% of Labour MPs and MEPs - 51 nominations.
Mr Corbyn was not at London's High Court when Mr Justice Foskett dismissed Mr Foster's claim.
Mr Corbyn said: "I welcome the decision by the High Court to respect the democracy of the Labour Party.
"This has been a waste of time and resources when our party should be focused on holding the government to account.
"There should have been no question of the right of half a million Labour Party members to choose their own leader being overturned. If anything, the aim should be to expand the number of voters in this election.
"I hope all candidates and supporters will reject any attempt to prolong this process, and that we can now proceed with the election in a comradely and respectful manner."
Mr McNicol said: "We are delighted that the court has upheld the authority and decision of the national executive committee of the Labour Party.
"We will continue with the leadership election as agreed by the NEC."