Wagner did talk to the authorities soon after Wood's drowning in 1981.
But he is the only person who was on the yacht the night Wood died who has not spoken to detectives as part of the latest inquiry, despite repeated requests and attempts, detective John Corina said.
Blair Berk, a lawyer for Wagner and his family, said the actor had co-operated with authorities since his wife died.
Detectives began re-investigating the case in November 2011, and have talked to more than 100 people, but Wagner has refused and Mr Corina said the actor's representatives have not given any reason for his silence. The detective's remarks provided new insight into the case that has remained one of Hollywood's enduring mysteries.
Earlier this week, coroner's officials released an updated autopsy report that had been under a security hold. It detailed why Wood's death had been reclassified from an accidental drowning to an drowning caused by "undetermined factors".
"Mr Wagner has fully co-operated over the last 30 years in the investigation of the accidental drowning of his wife in 1981," Ms Berk said in a statement. "Mr Wagner has been interviewed on multiple occasions by the Los Angeles sheriff's department and answered every single question asked of him by detectives during those interviews."
Ms Berk said after 30 years, neither Wagner nor his daughters have any new information to add. She said the latest investigation was prompted by people seeking to exploit and sensationalise the 30th anniversary of the death.
The authorities have not identified any suspects in the case.