FIRE SCENE: Victoria University Law School has been cordoned off after a suspected arson.

The southern hemisphere's largest wooden building was targeted in a suspected arson overnight.

The former government building, which now houses the Victoria University law school opposite Parliament in Wellington, this morning had a cordon in the carpark.

It is understood there was a suspected arson attempt outside the building early this morning, but it caused only minimal damage.

The Fire Service was called to the fire shortly before 1am, and central communications shift manager Murray Dunbar said investigators were looking into the cause.

The building is owned by the Department of Conservation and most of it is leased to the university for its law faculty.

Officially called Government Buildings, it was built in 1876 and once held New Zealand's entire public service.

According to DOC's website, it was built when provincial governments in New Zealand were replaced by a central administration.

It was built to resemble an Italian stone palace to "convey strength and stability" but, to avoid appearing extravagant, wood was used instead of stone.

That timber includes a large amount of kauri, which would be unthinkable now with kauri trees protected.

The last public servants moved out in 1990 and in the mid-1990s DOC undertook an extensive restoration of the building.