The state’s outgoing Correctional Services boss believes it’s "inevitable" a new prison or additional cells at existing jails will have to be built.

Peter Severin is moving to Sydney.

He says a new jail will be needed to cope with South Australia's growing prisoner population.

In an ominous warning to both the Government and Opposition, he predicts the state’s jails would be full by 2016.

The state government – in 2009 - scrapped plans for a new $750 million super-prison at Mobilong.