Papua New Guinea's Court of Disputed Returns has overturned the recent general election result in the Ambunti-Dreikikir Open seat.
The ruling means that the former Minister of Correctional Services, Tony Aimo of the National Alliance party, is the first candidate in the 2012 election to successfully challenge his loss.
The Electoral Commissioner has confirmed that the candidate who won the seat in the election, Ezekiel Anisi of the People's Progress Party, was found to be too young to contest the election.
The minimum age for a candidate to contest the PNG election is 25 and Mr Anisi had reportedly falsely claimed to be 26.
The court ruled that under organic law, Mr Aimo can be declared the MP-elect in Ambunti-Dreikikir rather than have the electorate go to a by-election.
The successful challenge brings the total number of MPs that the National Alliance has to 8 in the 111-member parliament.