The Central Bank has warned it is seriously concerned about a €9.3bn mortgage debt mountain in the main Irish banks.
A review of the most up-to-date data has found that a third of accounts for primary homes that are in arrears for more than 90 days are actually behind in repayments for almost two years.
They were worth €6.037bn at the end of June.
"The rapidly growing proportion of loans in this category is a source of serious concern, as these loans are effectively over two years behind on their repayments, and the scale of potential losses on these loans could be quite significant," the report found.
"It also indicates that the various resolution strategies implemented to date have, thus far, had little impact on longer-term arrears."
The value of mortgages in the buy-to-let sector which are behind in repayments to the same extent, 720 days, is €3.3bn.
The Central Bank revealed the scale of the problem after seeking more detailed data on arrears from Bank of Ireland, Allied Irish Banks, Ulster Bank and Permanent TSB.
The figures show the number of new cases of mortgage arrears is declining and lenders have been relatively good at arresting the fall of new households into debt.
But it warned that the amount of cases which are almost two years, or 720 days, behind in repayments continues to increase.
"This suggests that there is a significant quantity of distressed mortgages that are showing no signs of improvement and are simply transitioning through to the more advanced stages of arrears," it said.
The regulator revealed that arrears of more than 180 days experienced the most significant increase since it began keeping records in 2009. The value of these mortgages increased from €3.2bn to €15.6bn by the end of June.
Overall in the four years since arrears data started being calculated, the scale of debt-hit homeowners has grown to €18.6bn by the end of June - 17% of the market.
The Central Bank said the acceleration has been dramatic by international standards, even if the impact of the recession is taken into consideration.
The review found that the level of arrears of 90 days or more in the buy-to-let sector - which makes up makes up almost a quarter of the total outstanding value of mortgage loans - has soared.
It was valued at €8.7bn at the end of June - 29% of the total outstanding balance on all these type of investment accounts.
The Central Bank also examined how many mortgages have been restructured, whether put on interest only or other reduced payment options.
It found 23,500 mortgages, where the house is the principal residence, were restructured in the second quarter of 2013. More than half of these have been put on interest-only and reduced payment plans.
The Central Bank analysis found that early arrears figures have been on a downward trajectory since the end of 2011.
It warned that the various options offered by banks to resolve mortgage problems have so far either failed to tackle the problem effectively or not targeted the longer term debtors.
The data was published as part of the Central Bank's latest quarterly bulletin.
