Four backbenchers in the Vanuatu coalition government are among the MPs who signed a motion of no confidence against the prime minister, Sato Kilman.
The government backbenchers claim Mr Kilman's lead coalition government has failed to keep its promise to allocate political posts to their politicians.
On Friday, the opposition claimed it had the signatures of 28 of the 52 MPs in parliament.
The office of the speaker has now declared the motion of no confidence against Mr Kilman is in order and parliament is expected to meet within seven days to debate it.
Under Vanuatu's Constitution, parliament must meet within seven days, by next Friday, to vote on this motion.
Our correspondent says Mr Kilman now has seven days to convince his backbenchers and to meet their demands to avoid facing the motion.