A conservation group has apologised to Clive Palmer and agreed to pay his legal costs over claims it made about one of the billionaire's mines.

In January, WWF issued a media release expressing concerns that toxic waste was being mismanaged at Queensland Nickel's Yabulu refinery near Townsville.

The release said three ponds containing toxic industrial waste were at capacity and could collapse and create a major environmental disaster.

The allegations were repeated on radio by WWF spokesman Nick Heath.

In a letter of apology to Mr Palmer, the chief executive of WWF Australia said the organisation had received information on behalf of Mr Palmer that the concerns were unfounded.

"On the basis of that information, WWF and Mr Heath withdraw the suggestion that the dams as at January this year were in danger of collapse," chief executive Dermot O'Gorman wrote in the letter dated February 28.

"Also on the basis of that information, WWF and Mr Heath accept that works have been undertaken at the refinery to address the safety of the dams.

"WWF and Mr Heath accordingly apologise to Mr Palmer for any hurt caused by the publications in question."

WWF also agreed to pay the mining magnate's legal costs.

WWF said it would continue to be a strong advocate for Australia's environment, including the Great Barrier Reef.