Samoa's Leader of the Opposition says the government are trying to silence him, after he was arrested yesterday afternoon on defamation charges against the Prime Minister.

Samoa Police told RNZ Pacific that Tuilaepa Sailele Malielegaoi was held in remand for 24 hours, before being released this morning.

Tuilaepa, who was Samoa's Prime Minister for 21 years, told RNZ Pacific that this was an attempt by the state "to shut me up."

"They are feeling very embarrassed with my responses on issues raised by the media," he said.

"The reality of the leaks from (within) the government.... they have broken the law many times."

In April, Prime Minister La'auli Schmidt took Tuilaepa to court after the opposition leader made comments on social media accusing him and other ministers of misusing government money for personal and family expenditure.

Tuilaepa was ordered not to make these kinds of comments any longer, but at a press conference yesterday, he raised them again.

"I expressed my views on issues which the media had already reported," he said.

"I made my comments in accordance with my own belief that the court had given me the opportunity to continue to practice my right as the Leader of the Opposition."

Tuilaepa has now doubled down, claiming that money given to Samoa by New Zealand as restitution for the HMNZS Manawanui sinking was used to for the benefit rival FAST Party candidates in two Safata by-elections earlier this year.

"The money came for over a year, and the government withheld that money until the election period, and then distributed it out," he said.

"Independent candidates could not stand a chance, and the government was in the forefront of promoting the distribution of this money to bribe the voters."

He added that there is an active court case on the matter.

RNZ Pacific has sought comment from the government over the claims.