Mr Peters said NZ First had called for a register for foreign ownership of land and houses and had policy to stop non-residents "who are not New Zealand citizens from buying our houses and land, except if they first meet a stringent criteria related to New Zealand exports and economic interests".
"When the dust settles on election night 2014, New Zealand First will be in a strong position which makes the policies we stand for extremely relevant."
Labour also has a policy that if elected, it would block all purchases of existing property by people who did not live here, or did not plan to live here.
Mr Key said there was "a credible argument to see whether we should start collecting more data" on foreign ownership of housing.
However, it would not be straightforward to compile that data, "it depends on the structure that someone's buying that property in, it depends on what their intentions are".
He indicated that better data may reveal that much of the foreign purchases of New Zealand homes were not of a type that should be banned.
"On the best sort of data we can see, much of which is anecdotal, the majority of offshore buyers who buy a property, buy it because there is a fairly close connection in New Zealand. They intend to emigrate here, they have a family member here, all of those types of things, all of which boost the economy in lots of other forms."
National was not considering a ban in any case.
"That hasn't been the view that we've taken that that's been necessary at this point."
National believed supply side issues such as land availability were the main factor in rising house prices in Auckland as well as the city's increasing population.
Winston Peters' foreign land ownership register:
• NZ First has a members bill in Parliament's ballot that would require:
• The Registrar General of Lands to keep an electronic register of overseas persons who own land in New Zealand
• That would include name, nationality of the person, and the amount and value and location of land involved
• Any overseas person found to have failed to adequately provide that information faces a fine up of 25 per cent of the value of the land in question
• Each year Land Information NZ would have to report the number of registered overseas owners and the total amount and value of land involved.