Tarkine campaigners undeterred by ruling

Environmentalists challenging the approval of a mine in Tasmania's contentious Tarkine region have vowed they won't be deterred by a costs ruling against them.

The Federal Court has ordered green group the Tarkine National Coalition (TNC) to pay the legal costs of the federal environment minister and Venture Minerals.

It comes after the TNC last month lost a bid to have former environment minister Mark Butler's approval of Venture's Riley Creek project declared unlawful.

Lawyers for the TNC lodged an appeal against the ruling on Friday.

"We're not being deterred," TNC campaigner Scott Jordan told AAP.

"We've got strong grounds, we feel that the decision is unlawful and we feel that the question needs to be put before the full court."

The Commonwealth and Venture had reportedly been seeking up to $200,000 but the amount is yet to be confirmed.

Venture has also foreshadowed it could pursue individuals for costs.

"We've always taken a position of where we think there are strong grounds and we believe there is a high prospect of success we will proceed," Mr Jordan said.

Environmentalists argue the cumulative impact of three mines planned by Venture in the area on threatened species such as the Tasmanian devil was not taken into account by Mr Butler.

The Tarkine is home to the last wild devils free of the deadly facial tumour disease that has decimated 80 per cent of the species.

The Tasmanian government has put the value of the Riley Creek project to the state's economy at $40 million.