A sculpture of a New Zealand government minister crafted from cow manure has sold for $NZ3,080 ($A2,445) on an auction website.

The bust of New Zealand Environment Minister Nick Smith, sculpted as a protest by artist Sam Mahon, attracted 112 bids before being picked up by an anonymous buyer on Friday.

Mahon said he created the sculpture, and chose the medium, to protest what he considers Smith's too-soft stance on pollution created by dairy farms. He said the bust did not smell and would last forever.

"The sculpture has a hollow head, which is very fitting. It is highly polished and sits on the stand slightly to the right of centre," Mahon said.

Mahon gathered cow dung from an organic dairy farm, ground it in a coffee grinder, mixed it with a polymer resin and pressed it into a mold. He polished the sculpture with beeswax to create a finish that resembles bronze.

Smith joked about the tribute on Friday.

"Excuse the pun, but I would describe it as crap art," he said.