Overcrowding at a Cambridgeshire jail is "inhumane", according to the chairman of the independent monitoring board (IMB).
Littlehey Prison holds 726 inmates but doubling-up occurs in 62 single-prisoner cells, said the IMB report.
The prison service said at the end of May there were 946 inmates but Littlehey could safely take up to 1,056.
The dedication of staff and management at Littlehey was praised by the IMB.
The watchdog also had concerns about a new Young Offenders' Institution there.
It said it accepted its first inmates in February before many training courses and members of staff were in place.
Commenting on the 62 single cells at HMP Littlehey that are being occupied by two inmates, the chair of the IMB, Hazel Ainscough said: "We think it's inhumane to put two people in so small a space."
She said the inmates that were doubling-up had to share a toilet in the same cell and eat together.
The number of cells used in this way has not changed since the last IMB report in 2009.
The board is also worried about future budget cuts and how they could affect conditions at the prison.
Older prisoners concerns
The new Young Offenders Institution opened in February and will house 480 young men.
Mrs Ainscough said the new facility should have enough training and staff in place by the end of summer 2010 but that it should never have accepted inmates until they were in place.
The IMB annual report said HMP Littlehey has one of the oldest populations of prison inmates in the Eastern region, with 26% over the age of 50 and seven prisoners who are over 80.
It has reported its concerns about the lack of facilities and activities for older prisoners and said although it recognised that work is now underway it will continue to monitor this group of prisoners closely.
A Prison Service spokesman said: ""We look forward to reading the IMB report on HMP Littlehey. The IMB will receive a full response in due course."