Vanuatu's prime minister, Edward Natapei, and the executive of Vanuaku Party, have suspended the former lands minister and party rival, Harry Iauko.
This comes as the party is gearing up for this Wednesday's national congress in Tongoa, at which Mr Iauko planned to challenge Mr Natapei for the leadership.
The decision means that Mr Iauko will be prohibited from attending the congress.
Last week, Mr Iauko claimed to have the support of the majority of party subcommittees.
The Vanuaku Party constitution stipulates that the party president becomes the prime minister if the party forms the government.
Mr Natapei's move follows several failed bids by Mr Iauko to side with the opposition in bringing a motion of no confidence.