All three of the county's prisons remain overcrowded as a report from HMP Bure has said doubling up of prisoners in cells poses a 'serious risk'.
The Annual Report of the Independent Monitoring Board at HMP Bure outlined there were just two weeks last summer where there had not been 'the unsuitable double occupancy of 32 cells'.
They have now written to the prisons minister asking him to ensure all prisons, including Bure, operate within certified normal accommodation levels (CNA).
Every prison in the country has a CNA, which is the limit for ensuring a 'good, decent standard of accommodation'.
Since at least January all three of Norfolk's prisons have been overcrowded, with in excess of the number of prisoners in their CNA.
By November of this year, the most recent available figures, HMP Norwich were 139 prisoners above their CNA - or 122pc.
HMP Bure and Wayland were 48 and 68 prisoners above their CNA respectively, or around 108pc.
On prisoner accommodation at HMP Bure, the IMB said: 'Doubling up of residents in 32 of the cells in the recently built residential unit 7 was a concern highlighted to the minister last year.
'With the exception of two weeks in July this has continued unabated.
'Residents have endured cramped conditions, not enough space for property with only one chair and small table available to share.
'Residents and prison staff have raised their concerns on a number of occasions and the board considers the lack of space a serious risk as it may affect the ability to give emergency treatment in case of illness or accident.'
In October, HMP Bure was a single prisoner short of its operational capacity - the maximum number it can safely hold.
The same month, HMP Wayland had the absolute maximum number of prisoners it could safely hold - 843.
In August, Wayland had exceeded its operational capacity by three prisoners.
Andrew Neilson, director of campaigns at the Howard League for Penal Reform, has said: 'Cramming more people into prisons than they were designed to hold is a recipe for violence, drug abuse and mental distress.
'Bold action is needed to reduce the number of people behind bars and ease the pressure on other prisons.'
A Prisons Service spokesman said: 'All prisons in England and Wales are within their operational capacity which means they are safe for inmates and we will always ensure there are enough cells across the prison estate.
'Nonetheless, reducing crowding is a central aim of our modernisation of the prison estate. That is why we have committed to delivering up to 10,000 new prison places across the country and have already announced the building of two new prisons at Wellingborough and Glen Parva in Leicestershire.'
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