It was alleged that Greenpeace made arrangements with some oil companies to stop them from buying the by-product naphtha from Southern Pacific Petroleum's controversial shale oil project in Queensland.

The ACCC investigation concluded that there was no breach of the competition provisions of the Act because the oil companies which refused to buy the naphtha did so because of commercial reasons.

ACCC chairman Professor Allan Fels said there was no evidence that Greenpeace and the oil companies had come to any arrangement, agreement or understanding in relation to the purchasing of naphtha.

"Normally, the ACCC would not comment on any investigation which was under way," Professor Fels said. "However, in this case, there was publicity about the matter by other parties that an investigation was under way. It is now closed."