Vanuatu's former prime minister, Barak Sope, says he will go to court next month to force the government to allow him to return to his parliamentary seat.
The government said a by-election was required for the seat held by Mr Sope, who was pardoned for his fraud conviction two months ago after spending three months in jail.
The Speaker barred Mr Sope from parliament after a legal opinion that he needed to have lodged an appeal to the conviction within 30 days.
But Mr Sope says the pardon given by the President removed his conviction.
In addition, he says the law allows up to 150 days to make an appeal and he was in the process of doing this before he was pardoned.
Mr Sope says if the court does not reinstate him he will contest the by-election.
The opposition leader Willie Jimmy has already said other opposition parties would not stand against Mr Sope in such a vote.
The Electoral Commission says it has received no directive to prepare for a by-election.