More than 10m has been spent on repairs at Maghaberry Prison in just four years.
Spending peaked in 2012/13 at 3.2m and totalled almost 2m over the last financial year, according to figures released by justice minister David Ford.
The DUP's Sydney Anderson, a former member of the Prison Service who tabled the assembly question, said Mr Ford has "some serious questions to answer".
"It would appear to me that our prisons, in particular Maghaberry, are in a state of crisis," the Upper Bann MLA said.
"I have asked numerous written questions of the Department of Justice in recent weeks and the answers I have received have only confirmed my fears that our prisons are in deep turmoil."
Mr Anderson said the most recent major repair bill was caused by an arson attack within the prison grounds in April.
"When a repair bill of over 10m is recorded for Maghaberry Prison over the last few years as well as the 400,000 repair costs for this recent so-called 'small fire', one can feel nothing but a sense of a serious lack of confidence about the way prisons in Northern Ireland are being run.
Magahberry is Northern Ireland's only high-security jail and houses republican prisoners in a 'separated' regime.
Tensions between dissident inmates and staff have been high in recent years, with prison officer David Black shot dead on the M1 motorway on his way to work in 2012.
Mr Anderson claimed that not only are prisons "running up a titanic repair bill", they also appear to be understaffed and over populated.
He said Maghaberry has a recommend capacity of 988 prisoners, but in the last five years the population has risen by more than 200 to around 1,050.
"I am fearful that our prisons could be descending into a state of disarray. It is now imperative that the minister answer the question, is our prison system in a state of crisis?
"There must be no more beating about the bush, now is the time for answers. Public confidence is at an all time low with regards to the management of the Prison Service."
A Department of Justice spokesman said yesterday: The costs for repair and maintenance at Maghaberry have reduced considerably in the past number of years. The vast majority of costs are associated with planned and essential maintenance.
In 2012 the justice minister revealed that more than 1m was spent repairing damage caused to prisons by dissident republican 'dirty' protests.
The Prison Service also spent almost half a million pounds paying external companies to clean cells in Maghaberry.
