The family of a man who was found dead after going missing from Waikato Hospital want the hospital held to account.

They've laid a formal complaint with police.

Nicky Stevens was a patient at the Henry Bennett Centre when he died last month.

His father and Hamilton City Councillor Dave Macpherson says they want more than an apology.

He says it's a pretty high threshold to test against, but if someone's broken the law it should be checked out.