Wales' most senior judge is due to warn that a lack of prisons in Wales could be hindering offenders' rehabilitation.
Many people have to travel long distances to see relatives in prison
Sir Roderick Evans will call for more prison places in Wales saying families often have to travel long distances to visit relatives in jail.
This endangers family contact which is vital for prisoners' reintegration into society, the judge will tell a Law Society event on Thursday.
The prison service said it was building more prisons in England and Wales.
The call from Sir Roderick, Wales' most senior judge, comes the same week Parc Prison in Bridgend was criticised for failing inspection tests.
It failed to meet standards on a number of issues, including safety and prisoner work activity.
The judge believes there are "insufficient" prisons for male adults and young offenders.
There are no places at all in Wales for female prisoners.
The judge said: "North of Usk there is no prison of any sort in Wales.
"The result of this shortage of prison places is that large numbers of prisoners, whose homes are in Wales, are sent to prisons long distances from where they and their families live."
The judge said contact between prisoners and their families was "endangered" by the lack of prisons.
He added: "Arrangements for pre-release contact - which is so important for reintegration of prisoners into society - and their eventual rehabilitation is made more difficult."
One relative, Donna Jones, from Llangefni, said visiting her brother in a prison in Liverpool via public transport had put a "huge strain" on the whole family.
She told BBC News it took a bus, two trains and a taxi to get to HMP Altcourse in the Fazakerley area of the city.
"I'd have to wait then about an hour for me to be called upon to see my brother and then I got an hour with him in the visitors' centre," she said.
Sir Roderick Evans says Wales needs more prisons
"I'd try to visit about two o'clock in the afternoon. I'd set off about 9.30 in the morning and I'd come home maybe 8 o'clock at night... It took all day."
A prison service spokesman said the service was building more capacity in England and Wales to meet demand.
"Since 1997 we have built 19,000 new prison places and the further 8,000 additional places announced in the review are on top of the 80,400 capacity that we were already committed to by 2007," he said.
"The National Offender Management Service will be looking to identify suitable sites in areas of greatest strategic need."
The spokesman added that the prison service was also being "smarter" about how prison was used and focusing resources on where they would be most effective.