The first phase of the A534 dual carriageway has been built but a second phase involves two feeder roads to the north and south. Currently, lorries and cars have to travel on country lanes and through small villages to reach the estate.
Twenty objections to compulsory purchase orders were made in April and the inquiry is now being held by a Welsh Assembly Government inspector. Objectors began giving their evidence on Tuesday.
Wrexham County Borough Council leader Aled Roberts said: "The industrial estate is one of the largest in the UK, if not Europe, and it is still missing these link roads. They are necessary for the continued prosperity of north-east Wales."