The pardoned former prime minister of Vanuatu, Barak Sope, says the government will fail if it attempts to rewrite the constitution to reduce the president's power.
The government says there is increasing anger in Vanuatu after Mr Sope was pardoned last week, on medical grounds by President Father John Bani.
Mr Sope was jailed in July for three years after being found guilty of fraud.
Fr Bani has the right to pardon, but the government says there were other options if Mr Sope was ill.
It is to set up a commission of inquiry into the process and is also planning to change the constitution.
Mr Sope says they will not have the backing.
"They will never get to a certain majority, they don't have it. So I don't think they can change that part."
