Julie Bishop has sought an assurance from Nauru. Credit:Alex Ellinghausen The moves have only reinforced concerns over governance on the Pacific island nation. New Zealand's parliament last week passed a Greens party motion about Nauru expressed concern over allegations of interference with the judiciary and the treatment of opposition MPs. New Zealand's Foreign Minister Murray McCully has said he was "deeply concerned" and pledged to raise the issue with Mr Waqa in Sydney. "The situation in Nauru obviously has been boiling for some time, and this latest series of events, particularly around the restrictions being placed on members of parliament, is something that I think will attract more significant international attention," Mr McCully said. Ms Bishop has also spoken with Mr Waqa in the past fortnight after a local protest over the corruption claims turned violent and opposition MPs were arrested.

Ms Bishop said while it was a domestic matter for Nauru, she had conveyed concerns and sought assurances that due process and the rule of law would be upheld. Comment was sought from the Nauru government. Nauru, one one of the world's smallest countries, with an estimated population of 10,000, once boasted considerable riches from phosphate mining, only to see the wealth squandered. Steven Ratuva, director of the Macmillan Brown Centre for Pacific Studies at the University of Canterbury, said Nauru had struggled with an unstable political system since independence in 1969 and had undermined its own sovereignty by allowing Australia to set up its refugee processing centre for cash. Professor Ratuva said the "repression" by the current Nauru government was unwarranted and Australia and New Zealand should respond as a matter of principle.

"Unfortunately, Australia itself is directly embroiled in the mess and its hands are tied. New Zealand will not raise a voice because it might hurt Australia," he said. Fairfax Media has reported Australian federal police are expected to bring criminal charges after a long-running investigation into allegations Nauru's President Baron Waqa and Justice Minister David Adeang accepted bribes from an Australian company –claims both men deny. It follows a legal crisis last year after the government deported the magistrate and then refused to allow the Chief Justice to return to the country. Nauru's government insists it is upholding the law, and has previously accused "left-wing hypocrites" of unfair criticism and using nation as a punching bag. The government has said the several-hundred strong protest last month amounted to a riot, with parliament building vandalised and almost a dozen police injured.

Two opposition MPs, including the former president, Sprent Dabwido, have been refused bail and remain in custody – with a criminal conviction likely to rule them ineligible to again run for parliament. Another opposition MP, Roland Kun, was removed from a plane about to depart Nauru last month and has had his passport confiscated. The move has prevented him from reuniting with his children and Australian wife, who has also been stopped from returning to Nauru and is presently living in Wellington.