Foreigners have bought into more than 150,000 hectares of New Zealand farm land - almost the size of Stewart Island - in the past five years.

Among the investors are prominent billionaires noted for their luxurious assets, including one of the world's top superyachts.

Figures obtained by the Weekend Herald show Britons, Italians and Americans top the list of agricultural buyers since July 2005, followed by Israelis and Australians.

Most of the land they bought was for sheep, beef and cattle farming, including some high-country stations of up to 26,000ha in the South Island.

The release of the figures follows growing political controversy this week over the attempted purchase by Chinese interests of 16 dairy farms from receivers of the Crafar empire.

Prime Minister John Key responded on Wednesday by saying he would not like to see New Zealanders become tenants in their own country.

Asked if his preference was for the land to stay in New Zealand hands, Mr Key said: "As a general and broader principle, I think New Zealanders should be concerned if we sell huge tracts of our productive land."

Overseas investors must apply for permission to buy sensitive land - which includes rural holdings of 5ha or more - fishing quota or non-land assets worth more than $100 million.

One of the billionaire buyers listed in Overseas Investment Office decisions is understood to be Alexander Abramov, a Russian steel magnate who the Forbes rich list says is worth US$6.1 billion ($8.6 billion).

The decision records the Russian-owned Abramov Family Trust buying a 120ha farm in Northland last year.

Mr Abramov is said to own superyacht Triple Seven, a sleek and modern 67m boat with a cinema, gym and jacuzzi, which visited Auckland twice last summer.

He controls 22 per cent of Russia's total steel output as the chairman of Russian steel giant Evraz.

One of his partners there is fellow billionaire Roman Abramovich, a man known for his lavish spending as owner of British soccer team Chelsea.

The Overseas Investment Office document shows plans to build a high-quality residence at the beef farm in Helena Bay, just south of the Bay of Islands, which could be made available commercially to wealthy New Zealand and overseas clients.

It says he also plans to upgrade the farm, begin a stock-breeding programme and carry out environmental and historical preservation work.

Residents in the area told the Weekend Herald Mr Abramov had kept them well informed about his plans to build a "sizeable" family home with accommodation for staff.

The Russian has worked with the Conservation Department to build a pond for ducks and to protect reserves. "He's certainly dotted all the 'i's and crossed all the 't's," a resident said.

The property's manager, Chris Seel, would not confirm the identity of the owner, saying only that it was a getaway for a "fine" family who enjoyed their privacy.

Other wealthy farm owners include Israeli billionaire Shmuel Meitar, a co-owner of Walter Peak Station near Queenstown.