The NSW Greens MP Ian Cohen says he will have to pay more than $1 million in costs after losing a defamation case in the high court today.

The property developer Jerry Bennette sued Mr Cohen over comments he made during public meetings on the far north coast in 2001.

Previous court cases have heard Mr Cohen defamed Mr Bennette by saying he was a thug and a bully.

Ian Cohen says he will now look at how he can come up with the money.

"It's a pretty crushing blow, it's a difficult situation," he said.

"Contrary to a lot of popular opinion politicians don't quite make that sort of money.

"I will have to look at all my opportunities and really work it out with the bank manager and such like."