The Court of Appeal last week upheld a decision by the Speaker of Parliament to declare the Tanna MP's seat vacant.
This followed Mr Natuman's conviction for perverting the course of justice, for which he was given a two-year suspended sentence.
A by-election is expected to be held on Tanna within the next two months, with a date to soon be announced by the Electoral Commissiner.
Mr Natuman, who was deputy prime minister before his ejection from parliament, said his Vanua'aku Pati planned to contest the by-election.