Four former Prime Ministers are banding together to in a bid to have refugees allowed here - and they're from both ends of the spectrum.

Jim Bolger, Helen Clark, Sir Geoffrey Palmer and Mike Moore say there are "no rational arguments against us being more generous", and want the government to accept 500 more refugees "immediately".

The Welcome #500Now campaign says the four are supportive because of their time as Prime Minister. It says everyone should listen to what they have to say, given they come from different parties and different eras.

Sir Geoffrey Palmer, 33rd Prime Minister of New Zealand, said accepting more refugees is the right thing to do.

"In humanitarian circumstances like this, it seems to us that it would be a good idea for New Zealand to shoulder a bit more of the burden."

"It seems to me that in the name of common humanity, it's I think by far the worst refugee crisis the world has had."

Helen Clark, 37th Prime Minister of New Zealand, said another 500 refugees would be "do-able".

"The government would have to budget the money for it. The NGO community and host communities who support resettlement would need to gear up, but its do-able within the resources we have.

"We want to be seen as a good-hearted country. Not a soft-hearted country, but a good-hearted country that wants to pull its weight. And the pride and self-esteem that comes from that is also a positive," said Clark.

Clark said the big change since she was Prime Minister is the scale of the refugee challenge.

"The High Commission for refugees is very, very stretched. This is 2017, with 65 million forcibly displaced people around the world, a greater number than at the end of WWII."

Jim Bolger, 35th Prime Minister of New Zealand said "we are talking about one of the great humanitarian crises of our time and I know that New Zealanders will want to help solve that".

"You can't become tired of our common humanity. They are part of us. We all deserve the possibility of some kind of satisfying life."

When asked what to say to those who do not want to take more refugees in New Zealand, Bolger replied, "Just relax. Show a little generosity and humanity for those who are suffering."

Mike Moore, 34th Prime Minister of New Zealand, said that the joint call among four former Prime Ministers to accept 500 more refugees now might also be a sign they should have done more in their respective tenures.

"The fact that all these ex-Prime Ministers have come out for this is a sign that there's an underlying guilt amongst us that we haven't done enough. We are guilty. We haven't done our job. It won't hurt us. A couple of thousand refugees. Give me a break," said Moore.

Moore felt that our world ranking as 95th for the total number of refugees and asylum seekers we host per capita was shameful.

"Shame on us. We basically think we're better than we are. But we're not.

"One of the great joys of my life was being Labour Leader and people coming up in Wellington and saying, 'I'm one of Peter Fraser's babies. That is fabulous," Moore said.

"We should welcome 500 now. They'd be fantastic New Zealanders," Moore said.

The government announced last year it was upping the Refugee Quota from 750, to 1000 places a year by next year.