Environmental pressure group WWF urged Bulgaria on Tuesday to withdraw planned changes to its forestry legislation which would relax rules on building ski runs and facilities in protected areas.

"The proposed amendments ... would allow for the construction of ski runs and ski facilities without changing land use," WWF said in an open letter to Bulgarian Prime Minister Boyko Borisov.

"Furthermore, they would allow the acquisition of building rights on public land without tender and for an indefinite period," they added.

"Bulgaria is home to many of Europe's outstanding natural treasures and has a special responsibility to preserve this wealth not only on behalf of Bulgarians but also, as a member of the European Union, on behalf of all Europeans."

The proposed changes, which are yet to be approved by Bulgaria's parliament, have already sparked several protests from local environmental groups and nature lovers in the capital Sofia.

In particular they slammed recent efforts by ski run operators on the Vitosha mountain near Sofia and the Bansko ski resort in the southern Pirin mountain to expand existing ski runs and facilities to protected nature areas.

WWF also said Tuesday it was "concerned by the manner in which decision making on the proposed legislation has been taking place."

The changes were adopted by the government "in four days over the Christmas holidays and in violation of the required two weeks for public consultation," WWF charged.