The Ministry of Justice has drawn up plans for a two-storey custody suite at Wrexham Magistrates' Court.
Cells used at neighbouring Wrexham Police Station are due to be decommissioned in the summer.
North Wales Police is due to demolish its tower block police station site and relocate to new premises.
Wrexham MP Ian Lucas has long been pushing for a commitment from the UK government to invest in the court buildings in the town centre.
A planning application submitted to Wrexham council said a custody suite was "essential to the operation" of the law courts.