There are growing calls for the government to ramp up the pressure on Australia as more details emerge about New Zealanders being detained on Christmas Island.

Photo: AAP

There have been suggestions up to 75 New Zealanders and Pacific Islanders are being held on Christmas Island but Australian authorities refuse to discuss numbers.

Radio New Zealand News has been told more and more New Zealanders have been arriving, including about 20 in the past few days.

Prime Minister John Key said he wanted Australia to provide better information about the treatment of people it was deporting to New Zealand.

Mr Key said he had heard anecdotal accounts but had no idea how many people might be there, and Australia should provide more information.

Photo: RNZ / Alexander Robertson

Under new rules introduced late last year, anyone who is not an Australian citizen and has served more than a year in prison in their lifetime is liable for deportation.

Political parties here say the New Zealand and Australian governments have been happy to talk up the trans-Tasman relationship when it suited them, but this situation undermined all the rhetoric.

Labour's Foreign Affairs spokesperson David Shearer said the situation was simply unacceptable.

"Australia is dumping on New Zealand some of the laws that they've put in for other reasons, to satisfy their domestic constituency and we're, in a sense, carrying the brunt of it."

He said the Government should have much greater detail about the number of New Zealanders who are now there.

'They should know exactly what the situation is and they should be making representations to the Australian government right now, and they should be pretty forceful ones, quite frankly.

"Because if an Australian was in the same situation in New Zealand they would get Rolls Royce treatment compared to what New Zealanders are getting in Australia."

Photo: Supplied/The Green Party

Green Party global affairs spokesperson Kennedy Graham agreed the government must act.

"I'm not sure exactly what they have said privately to Australia, publicly all the Prime Minister seems to have done is scratch his head and say he had no idea.

"Well fair enough, now that we have an idea we need to turn it around very quickly in terms of new policy."

Labour's David Shearer said three Australian politicians, both government and opposition, appeared before the Foreign Affairs Defence and Trade select committee this week, and were given a blunt message to take back to their own parliament.

"This is a situation which is festering. We don't want it to get any worse, we don't want it to affect our relationship - get in and nip this in the bud before it becomes an issue because it will become an issue."

Mr Graham said the application of the new rules to New Zealanders was appalling.

"It would never be tolerated by Australia here. It displays a contempt, I think, Australia seems to have if not for New Zealand then some New Zealanders in Australia."

Photo: RNZ / Diego Opatowski

Peter Dunne, the leader of government support partner United Future , said these actions struck at the heart of the two countries' relationship.

"We're supposed to be family, kith and kin - all that sort of thing - and yet we're seeing our people treated the same way as other overstayers or other people about to be deported, and at the same time both governments go out of their way to talk about our special relationships.

He said because of that relationship, New Zealanders should get different treatment.

"Where we have a free flow of people between our country, where a lot of New Zealanders will go back and forward to Australia many times in their working careers.

"And it just seems to me that treating the people in New Zealand who are about to be deported to this country the same way as a whole lot of other people is, I think, a little bit unfair."

Mr Key said he was also worried Australia intended to deport people who had committed very minor offences, and he intended raising the issue with new Australian Prime Minister Malcolm Turnbull.

"There are people that are potentially going to be deported to New Zealand now, under the new rules Australia are implementing, that are at a very low threshold of criminal activity but [have] no community of interest with New Zealand."