Wellington City Council has been stripped of the power to sell or exchange town belt land.
The Wellington Town Belt Bill, sponsored by local Labour MP Grant Robertson on behalf of the council, passed into law yesterday, immediately adding 120 hectares to the green space in the city.
The latest addition brings the town belt to 520 hectares.
The new law restricts the council's powers, but makes it easier for it to add land to the reserves.
Mr Robertson said it provided greater protection for the land, which was previously governed by a trust deed signed in 1873.
He said the law also outlined what the land can be used for, which is public recreation.
"The bill says that public recreation is essentially outdoor activities that all members of the public can be a part of, that protects the natural environment, protects the purpose of the town belt."