Tonga has appointed only its second commoner Prime Minister in history, in a move observers hope will promote democracy in the Pacific kingdom where commoners hold little power.

Dr Fred Sevele was named Acting Prime Minister yesterday, following the sudden resignation of Prince 'Ulukalala Lavaka Ata at the weekend.

The Prince's resignation came without warning, but public reaction has been muted as the country was battening down for Cyclone Vaianu.

Tonga's Government information unit said Crown Prince Tupouto'a accepted the Prime Minister's resignation on Saturday.

Prince 'Ulukalala, the youngest son of King Taufa'ahau Tupou IV, had also given up his other Cabinet portfolios.

Local radio described Dr Sevele as a friend of the Crown Prince.

The first commoner to take up the position was Baron Vaea, who served as Prime Minister from 1991 to 2000.

Auckland-based journalist and broadcaster Sefita Haouli said last night that the appointment of Dr Sevele was a sign that the last kingdom in the Pacific was moving towards a more democratic system.

Mr Haouli said he had known Dr Sevele for 30 years, and considered him a "very cosmopolitan" man who had travelled "widely".

Dr Sevele was one of the first two commoners appointed to the Cabinet when the monarchy ended its tradition of handpicking all ministers and was given the labour, commerce and industries portfolios last March.

But Mr Haouli said the elevation to Prime Minister would bring a big workload for the former exporter, who as an MP has battled to tame the country's rampant public service.

"This promotion comes with a lot of expectation.

"He's expected to deal with these issues, but he would probably be better suited than any of the ministers in the House not appointed by the people but by the King.

"He's nobody's lackey. I think he's capable, but he has got a lot on his plate."

Mr Haouli said Dr Sevele would have trouble reconciling the needs of the economy with the desires of private enterprise, but was "very in favour" of entrepreneurs.

Dr Sevele had "worked well" with the pro-democracy faction in the Parliament, and had previously supported attempts to have all members of Parliament elected.

But Mr Haouli said the Prime Minister was still totally subservient to the King.

The post was granted certain statutory powers by legislation, but Dr Sevele would be forced to abide by the rulings of the Privy Council.

"In Tonga, the Privy Council is the King and his ministers."

Dr Sevele would need to learn the boundaries of his authority, and what the King wanted done.

However, Mr Haouli was sure Dr Sevele would lock horns with the King on issues he felt were important to him and the Tongan people.

"He is very much his own man."