The Magistrates Court will now sit in Perth seven days a week in a bid to clear out police lock-ups.

Before today, sittings were held on Mondays through to Saturdays, with those arrested Sunday having to wait in a holding cell overnight for their court appearance.

The Sunday court sittings will be held at the new Perth Police Complex in Northbridge.

It was revealed last September that the court had been sitting idle six-and-a-half days a week due to a lack of security.

WA Attorney General Michael Mischin said the court was expected to have to deal with up to 40 alleged offenders each Sunday.

Sunday court sittings would also hear matters at regional police lock-ups around the state via video-link.

Sunday court an election promise: Mischin

Mr Mischin said the start of Sunday court hearings fulfilled an election commitment.

"It allows for not only the clearing of the lock-ups, and the relief on the police of having to look after offenders until Monday mornings, but allows a more sensible allocation of cases into the future," he said.

"We expect about 30 to 40 people would be processed on any Sunday and $2.7 million has been committed over the next three years to meet this initiative."

He said a magistrate had the option to remand offenders in custody, so that they could be taken to metropolitan prisons, or release them on bail to appear in court at a later date.