Mr Key said there were 14,135 people on super who had arrived when they were 56 or older - and the largest group of those was from the United Kingdom which has a reciprocal super agreement with New Zealand.
"At the margins, we are giving some people the benefit of New Zealand superannuation when they haven't made a significant contribution, if any, to the New Zealand economy, but their family members are in work. But it's at the very margins."
He said he trusted his own figures more than Mr Peters' figures - partly because Mr Peters had said his source was an unnamed senior figure in the Chinese community.
"We have an army of officials and he has some guy hanging out in Dominion Rd in a Chinese restaurant he wants to close down. That's what he seemed to say in the paper. I'll back my officials."
However, Mr Peters said Mr Key's figures were "nebulous nonsense".
Although the issue was first raised with him by a senior member of the Chinese community, his 22,000 figure was a "conservative estimate" based on a 2002 Department of Labour report and further calculations to update it. He said 100,000 people had arrived under family sponsorship schemes in the last 15 years, including 25,000 from China with which New Zealand did not have a reciprocal agreement for super.
When other countries without such an agreement were included, he said there would be at least 22,000 eligible for super from a country without a reciprocal agreement.
"I've checked it again with my informants on this matter and researchers, and this is a very conservative figure."
Mr Key said that the Government had tightened the rules for older migrants entering New Zealand to join their family here, by giving priority to those who waived their rights to super. He said overall migrants paid $3.3 billion more in taxes than they cost in services such as health, welfare and super - figures taken from Department of Labour research into the 2006 Census.
That showed immigrants contributed $8.1 billion to the Government coffers, including income tax of $4.8 billion a year, GST and other taxes. The cost to the Government in services such as superannuation, benefits and health and education was $4.8 million.
Mr Peters rejected any suggestion that commonality on the retirement age was bringing the two leaders closer.
"He's just too scared to move because he knows how appalling their practice has been in terms of saying one thing before the election and doing something else."
Mr Key said Mr Peters' claims were "typical Winston".
"Beat the drum about Chinese migrants and you might get your poll numbers up a bit. It's pretty cynical."
