Royal Bank of Scotland Group (RBS) has agreed to pay $1.1bn to the National Credit Union Administration (NCUA) for allegedly selling toxic mortgage securities to credit unions in the run-up to the financial crisis.

The settlement resolves two residential mortgage-backed securities (RMBS) lawsuits filed on behalf of US Central Federal Credit Union and Western Corporate Federal Credit Union.

The settlement will not affect the bank’s common equity Tier 1 ratio and will be substantially covered by £3.8bn ($4.9bn) of existing provisions, the British lender said.

At the same time, the bank also highlighted the requirement of additional provisions.

“As previously stated, RMBS litigation and investigations may require additional provisions in future periods that in aggregate could be materially in excess of the provisions existing as of 30 June 2016,” RBS said.

RBS is currently defending nearly 15 civil lawsuits in the US, with some filed by the Department of Justice and the Federal Housing Finance Agency.

“RBS continues to litigate various other RMBS-related civil claims identified in its disclosure, including those of the Federal Housing Finance Agency, and to respond to investigations by the civil and criminal divisions of the U.S. Department of Justice and various other members of the RMBS Working Group of the Financial Fraud Enforcement Task Force (including several state attorneys general),” the bank said.

In 2015, RBS agreed a $129.6m settlement with the NCUA to resolve a similar lawsuit. Overall, the NCUA has collected $4.3bn in settlement from banks over mis-sold mortgage securities.