Wellington, July 13 NZPA - Foreign Minister Murray McCully has called his Fijian counterpart to protest the expulsion of Australia's acting high commissioner to Suva, which he says was a "completely unjustified" action.

Sarah Roberts was ordered to leave today, with self-appointed Prime Minister Voreqe (Frank) Bainimarama accusing Australia and New Zealand of trying to stymie a regional summit of the Melanesian Spearhead Group (MSG) which was to have been held in Fiji.

The five-member MSG group, which includes Vanuatu, Papua New Guinea and the Solomon Islands, said it was cancelling this month's summit in military-run Fiji over concerns about democracy and "good governance".

Australia had lobbied for the summit to be postponed, and a Fiji government statement said the expulsion of acting high commissioner Ms Roberts was a direct result of "interfering with the internal affairs of Fiji and conducting unfriendly acts".

Mr McCully said on Radio New Zealand he had called Fiji's Foreign Minister Inoke Kubuabolo "to convey both personally and formally my deep concern and disappointment that they have chosen to follow this course".

He said he had asked the Ministry of Foreign Affairs to call in Fiji's representative in New Zealand "to communicate our concern at the unjustified expulsion of an acting head of mission".

Ms Roberts is the second senior Australian diplomat to be expelled from Fiji in less than a year after the high commissioner and his New Zealand counterpart were removed last November over alleged interference in Fiji's judiciary.

Australia and New Zealand have been among the harshest critics of Fiji since Commodore Bainimarama led a bloodless coup in 2006 and later put back a return to democratic elections from 2009 to 2014.

Cdre Bainimarama, speaking from South Korea, was quoted by the Fiji Sun as saying the summit cancellation was a threat to the future of the MSG, the only major regional group from which Australia and New Zealand were excluded.

"I'm disappointed," Bainimarama said, claiming Vanuatu Prime Minister Edward Natapei was pressured to axe the summit by Australia and New Zealand.

"Australia and New Zealand are trying to embarrass Fiji by dissolving the MSG. If there is no MSG then MSG leaders will be reluctant to come forward and discuss their issues and problems."

Mr McCully issued a statement today saying the explusion was "counterproductive on almost every level" and he rejected any suggestion that Australian and New Zealand pressure was the reason for the collapse of the MSG summit.

"It is deeply insulting to Vanuatu Prime Minister Natapei to suggest that his decision to defer the MSG meeting was made because of pressure from New Zealand and Australia," Mr McCully said.

"Prime Minister Natapei needed no help from New Zealand or Australia to work out that democratic principles should prevail within the region."

Fiji Foreign Minister Inoke Kubuabolo has also accused Australia of undermining his country's sovereignty and weakening its economy.

"The MSG leaders' summit and associated meetings are very important to Fiji and the Pacific countries given the opportunity it presents to expand ties in trade, tourism and peoples' exchange."

Kubuabola said Fiji was being subjected to "undue pressure and frustrated in its efforts by the use of economic, financial and political clout of Australia."

Since the 2006 coup, Fiji has been suspended from the Commonwealth and the 16-nation Pacific Islands Forum and has been hit with sanctions by the European Union and countries including the United States, Australia and New Zealand.

Canberra does not intend to expel Fiji's sole diplomat in Australia.