Last week the regulator published its further analysis of the 250,000 borrowers currently placed with inactive, closed or unregulated lenders.
This confirmed the initial estimate that only around 14,000 borrowers could materially benefit from the changes to its affordability assessment rules brought in last year.
As part of the analysis, the FCA said it found a group of around 80,000 borrowers who were either in arrears or had been in arrears in the last 12 months.
Mortgage Solutions asked the FCA if it had conducted an assessment of these borrowers and what some of the key characteristics of this group were.
The regulator could not provide any detail about these borrowers as it has not done any analysis of this cohort.
Mortgage Solutions understands that the FCA analysis only focussed on the mortgage prisoners that would be eligible to move to a new deal under its new rules.
However, those in arrears are potentially the most vulnerable borrowers within the whole group of mortgage prisoners and may be facing the highest interest rates of all.
The FCA did not answer if it has any plans to analyse this group in the future.