The Royal Bank of Scotland has added another £250m to its compensation pot for the mis-selling of payment protection insurance.
According to the group's third quarter financial results, RBS has increased its provision to reach £2.6bn (€3.07bn, $4.2bn) for the mis-selling of PPI.
Out of the cumulative charge in respect of PPI, £1.9bn (73%) has already been paid in redress and expenses to customers, as of 30 September 2013.
Of the amount prior to the additional £250m set aside, the bank says £2.3bn relates to redress and £300m to administrative expenses.
"The remaining provision provides coverage for approximately 10 months for redress and administrative expenses, based on the current average monthly utilisation," said RBS in a statement.
"There are uncertainties as to the eventual cost of redress which will depend on actual complaint volumes, take up and uphold rates and average redress costs.
"Assumptions relating to these are inherently uncertain and the ultimate financial impact may be different than the amount provided. The group will continue to monitor the position closely and refresh its assumptions."
Banks have so far set aside just over £17bn to deal with mis-sold PPI.
It has become the most expensive consumer scandal in British history.
PPI was originally designed to provide loan repayment cover, should the customer fall ill, lose their job or have an accident.
However, millions of customers complained because they never wanted or needed the policy in the first place.
According to Financial Conduct Authority data, the issue of PPI raked in the most complaints for banks between January and June 2013.
Some 1,786,626 complaints were opened during this period and PPI accounted for 61% of new complaints.
On 29 October, Lloyds Banking Group revealed that it added another £750m to its PPI compensation pot amid a slower-than-expected fall in complaints.
According to the group's third quarter interim management statement, Lloyds revealed the total amount it has set aside for PPI compensation has reached £8bn, as it fights to tackle the flood of complaints.