A bill tightening controls on foreigners buying sensitive land but loosening business investment rules should be rewritten so it's harder for foreigners to buy land and companies, a parliamentary committee has been told.

The Overseas Investment Bill abolishes the Overseas Investment Commission and shifts its role to Land Information New Zealand.

It also requires non-resident foreign land buyers to show how they would manage historic, heritage, conservation or public access factors.

But the bill also increases the threshold for approval of business acquisitions from $50 million to $100 million.

Hugh Barr told the finance and expenditure select committee on behalf of the Deerstalkers Association that the back-country was being bought by foreigners as "private game parks" that excluded New Zealanders.

Foreigners should be stopped from buying any pastoral or other Crown leases.

"Foreigners often have no commitment to New Zealand or New Zealanders. They come to speculate and drive up land prices, to the detriment of New Zealanders."

The price of $21.4 million paid last year by Canadian singer Shania Twain for pastoral leases of Wanaka's Motatapu and Mt Soho stations was at least four times higher than any realistic grazing lease cost for the amount of stock the properties had.

"These properties are bought as international trophies, because New Zealand is one of the few places that allows foreigners to buy 5000ha to 50,000ha blocks of mountain land. I bet she can't buy such land in Canada," Dr Barr said.

The Campaign Against Foreign Control of Aotearoa (CAFCA) called for the bill to be totally revamped.

CAFCA's Bill Rosenberg said New Zealand went to great lengths to ensure immigrants had skills and were of good character.

"Why do we not do the same for potentially vastly more damaging corporations?

"The regime New Zealand has run for the last two decades for corporate investment is one of virtually non-existent control - and the Government is now proposing to reduce that control even further."

CAFCA cited 19 examples of overseas purchases of companies and land in the last two years worth between $50 million and $100 million. Many were highly significant for economic, environmental or social reasons, the submission said.

Under the new provisions none would require the regulator's approval.

The Green Party said the threshold for approval for foreign buy-ups should be reduced to $10 million and all land sales to foreign firms and individuals who are not permanent residents should be prohibited.

But Gerald Fitzgerald, a partner in law firm Kensington Swan, said too many controls could "cut off our nose to spite our collective national face".

In the bill

* Foreigners wanting to buy land but not live here will need to show how they will manage historic, heritage, conservation or public access issues, as well as any economic development planned.

* Maximum fines will be increased from $30,000 for individuals and $100,000 for companies to $300,000 for both.

* Threshold for approval of business acquisitions doubles from $50 million to $100 million.