A "significant" number of people could find themselves in financial difficulty when the interest rates start to rise again, according to the Bank of England.
The central bank's deputy governor Paul Tucker has requested regulators to investigate the issue as soon as possible.
Currently the base rate is 0.5 per cent, and has been at this record low since March 2009, but should rates rise by just one percentage point - to 1.5 per cent - the bank said households accounting for nine per cent of mortgage debt would need to earn more money or work longer hours.
According to the bank's Financial Stability Report "significant cohorts of UK borrowers could experience financial difficulties" if rates did rise.
However, Sir Mervyn King, in his last public appearance as Bank of England governor, suggested it would be a long time before interest rates increased and world economies were far from a return to normal.
By Gary Cooper