Anglesey's council leaders have added their backing to calls for a prison to be built in north Wales.
There are five prisons in Wales, but all are in the south
The council's executive said it was "imperative" that the jail's site should be both "central and strategic" to ensure the widest benefits.
Council leader Councillor Gareth Winston Roberts is writing to the UK prisons minister David Hanson, pressing the case for a prison in the area.
The UK Government is reviewing the demand as part of an overall review.
In June, the Welsh affairs committee proposed that a new jail for up to 500 inmates should be built in north Wales, helping to ease overcrowding in prisons in England and allowing inmates to serve their sentences close to home.
The Criminal Justice Board - which says 700 inmates from north Wales are housed at English prisons - has asked for views from local authorities on potential sites.
The old Firestone rubber factory in Wrexham, the Friction Dynamics plant in Caernarfon, and the former Shell site at Rhosgoch on Anglesey are among sites mentioned as possible locations.
Mr Roberts said: "There are also important social and economic benefits, and the need for bilingual custodial provision for prisoners has already been highlighted by the Welsh affairs committee."