A Labour MP believes Jonathan Coleman when he says he didn't know about problems at Middlemore Hospital but says he should have.

The former Health Minister says he had no idea several buildings at the South Auckland hospital had rot and mould problems.

MP Stuart Nash told Mike Hosking the fact Coleman didn't know is the issue.

"I just don't think Jonathan was doing his job properly. He should've known and the reason he should've known as he should have had a relationship with the DHB chair where he or she could have picked up the phone and said, minister, we have a bit of an issue."

LISTEN TO THE FULL POLITICS WEDNESDAY DISCUSSION WITH STUART NASH AND MARK MITCHELL ABOVE