Vanuatu has backed changes in a referendum aiming to end political instability that saw the Pacific nation elect three prime ministers in a month.

The result, announced on Wednesday, will allow changes to its constitution that supporters hope will end the revolving door that brought on protests last year.

Vanuatu's Prime Minister Charlot Salwai called the referendum after growing public frustration at MPs who spent weeks in political deadlock while the archipelago nation recovered from recent twin tropical cyclones and the economic impact of COVID.

Voters were asked in the referendum — held over several days in late May and early June — whether they supported reforms aiming to stop MPs crossing the floor of parliament. 

It was Vanuatu's first referendum since it gained independence from Britain and France in 1980.

One of the two reforms put to voters would mean MPs lose their seats if they are expelled from their party.

Under the second reform, independent MPs would have to affiliate with a political party, or have their seats vacated.

Griffith University expert in Pacific politics, Tess Newton Cain, said the underlying objective is to strengthen political parties, and incentivise being a member of a political party to try increasing stability.

The first reform won 59 per cent support in the referendum, while the second reform won nearly 58 per cent backing from voters.

The voter turnout is yet to be announced although about 90,000 people cast valid votes on each of the amendments.

Ni-Vanuatu cast their referendum votes across the archipelago nation of 320,000 people, and at polling stations in Australia and New Zealand for seasonal workers and other members of the diaspora.

Anna Naupa, an expert in Vanuatu politics and government, said the referendum result signalled that a majority of voters wanted change.

"It's not a slim majority. It's a decent majority that signals yes to both of the referendum questions," she said.

The referendum result will bring the reforms into effect, although how they will be administered is yet to become clear.

Despite the referendum result, some political leaders and experts say the reforms alone won't stabilise Vanuatu's politics.

Change 'under the red roof'

Vanuatu made international headlines between August and October last year for a period of acute instability "under the red roof", as its parliament is sometimes known in the country.

MPs discarded and elected a series of prime ministers, one of whom served for only 30 days.

The churn in parliament came as MPs switched allegiances between opposing political sides — sometimes changing back in a matter of days amid ongoing negotiations. 

It's a political practice notorious in Vanuatu and known in its national language as "jump-jump".

Parliament passed reforms aiming to stop MPs crossing the floor in December, after protesters marched peacefully and presented Mr Salwai with a petition calling for stability.

However, the changes also required majority support in a referendum, and Mr Salwai announced a vote in December, giving electoral officials six months to arrange it.

While government MPs backed the changes in parliament, opponents emerged early this year including former prime minister Ishmael Kalsakau — whose own government fell in a vote of no confidence last year.

Mr Kalsakau said his constituents in the capital Port Vila had questioned whether Vanuatu had considered other ways to end instability without restricting democratic rights, as proposed in the reforms.

"What is the actual root cause of instability? If you look at our history … it's all about power struggles," he told ABC's Pacific Beat last month.

"We could be accused of tampering with those rights, negatively against the citizens, in a matter that concerns just members of parliament frolicking in the parliament, in a manner that could be resolved by other means."

He also called for a delay in the vote amid reports of a lack of public awareness about the changes being proposed.

Pacific politics expert at Victoria University of Wellington, Jon Fraenkel, also criticised the proposals, saying they gave more power to party presidents and the speaker of parliament, and could be abused by governments to shore up their own position.

But supporters of the changes say they are necessary to stabilise the parliament.

'A starting point' for change

Members of the public say Vanuatu's regular changes in government have slowed progress in developing its economy, distracted ministers from addressing community needs, and added to challenges brought by natural disasters and climate change.

While some doubt the referendum result will end the country's political churn, community leaders and experts see potential for other reforms that could bring more stability.