Cambodia's Constitutional Council on Thursday said it had rejected an appeal by the country's sole opposition party against its disqualification from an election in July.
The Candlelight Party, a weakened reincarnation of a popular opposition party that was dissolved in 2017, was disqualified from the July election 10 days ago over an issue with its registration paperwork.
The decision means the ruling Cambodian People's Party (CPP) will run largely unopposed.
The tribunal's president Chhun Lim at a press conference said the appeal was deemed not legal and the decision was final.
The Candelight Party was disqualified from the election on May 15 for submitting a registration document that was a photocopy rather than an original.
Rights groups have expressed outrage over what they call an attempt by long-serving Prime Minister Hun Sen to crush his democratic opposition.
Officials from the Candlelight Party could not immediately be reached for comment on the tribunal's decision.
Just over a year old, Candlelight was the only party running against Hun Sen's ruling CPP, which has monopolised all levels of politics since the 2017 dissolution of its popular rival, the Cambodia National Rescue Party (CNRP).
Scores of former CNRP members have been detained or convicted of crimes, many in absentia having fled into exile amid Hun Sen's sweeping crackdown on critics.
Hun Sen has previously said the CPP will dominate politics for up to 100 years.
Sam Rainsy, CNRP's self-exiled co-founder, last week dismissed what he said would be a "fake and sham" election.
(Reporting by Prak Chan Thul; Writing by Martin Petty; Editing by Kanupriya Kapoor)