According to the BBC, the Ombudsman received 30,301 PPI complaints in the final quarter of last year, 57% more than the 19,259 received in the previous three months.
Of these, the FOS found in favour of the customers in 68% of cases.
The rise led to a 10% increase in the total number of cases dealt with by the Ombudsman in Q4, which received a total of 55,907 complaints in the period.
Payment protection insurance complaints now make up 54% of the FOS’s entire workload, far outstripping complaints related to other products.
Credit cards, current accounts and mortgages between them accounted for just 18% of all complaints received between October and December last year.
Earlier this month, the FOS proposed a new funding system for firms that receive a large number of complaints.
The “largest users” of the FOS refer more than 2,000 cases to it each year.