West Australian Treasurer Troy Buswell has apologised over an affair with Greens MP Adele Carles but says he intends to stay on as treasurer.

Facing the media in Perth today, Mr Buswell confirmed the affair and said he had deeply hurt his family and many others.

Sorry ... Troy Buswell. Credit:Australian Financial Review

"My lack of judgment in this matter has disappointed a great number of people," he said.

"I would particularly like to apologise to my wife and boys."