A huge hike in journalists' visa fees for Nauru is designed to cover up how Australian taxpayers' money is being spent on the "cruel" detention centre there, the Greens say.

A spokeswoman for Nauru's government has told the ABC the cost of a single-entry media visa is due to rise from $200 to $8,000.

Hundreds of asylum seekers who have arrived in Australian waters by boat are held at a detention centre on the island, and the Greens say the sudden price rise is an attempt to cover up what is happening there.

"This is of course part of Tony Abbott's strategy to shut down public information about how Australian taxpayer money is being spent on the cruel and harsh detention camps on Nauru," Greens Senator Sarah Hanson-Young said.

"It's designed to make it difficult for the media to access Nauru and to get information back to Australia.

"This is just more fuel to the fire of Tony Abbott's media blackout strategy rather than anything to do with what is best for humanitarian needs of refugees."

The Government has batted away the claim, with a spokeswoman for Immigration Minister Scott Morrison telling the ABC: "This is a matter for the government of Nauru."

A spokesperson for the Department of Foreign Affairs and Trade added: "While this is a matter for the Nauru Government, we would hope that it would reflect on the implications of any such cost increase."

Only three or four media visas were granted last year, according to Nauru's top visa officer Ernest Stephen, who spoke to current affairs website The Global Mail.

The site also reported that there was a notable increase in the issuing of media visas in the weeks after the former Labor government reintroduced offshore processing for asylum seekers in September.

A damning United Nations report into conditions on Nauru, released in November, found asylum seekers lived in harsh conditions with little privacy and limited services for those suffering from trauma and the effects of torture.

But Australia's former immigration minister, Chris Bowen, said services at the detention centre were adequate.

Another attempt to 'censor the media'

Mathew Batsiua, a member of Nauru Opposition Group, says the new rules, expected to come into force this week, are a Nauru government tactic to censor the media.

"They certainly bully our local media in terms of what they can show, who they can interview, and this is another illustration of that kind of behaviour in terms of bullying media and avoiding accountability," he said.

"It is an alarming trend, and this [Nauruan] government since they've come in has slowly shown its true colours - they are not interested in true accountability; they are not interested in true transparency.

"They talk hot about it, but it's all lip-service. When it comes down to the crunch, they won't baulk in trying to censor media, and this latest policy ... is another illustration of that kind of behaviour and conduct."

He said his party was opposed to any policy that attempts to curtail any transparency of their actions.

"This hiking up of fees for journalists coming in to Nauru is a step in that direction, and we think that it's the wrong move and we're certainly opposing it."

Visitors from Commonwealth countries travelling to Nauru for holidays can be granted visas on arrival which cost $100.

The journalists fee will not be refunded if the application is unsuccessful.