State-backed Royal Bank of Scotland slumped to a loss of £446 million in the first quarter, it revealed today.

The lender, 80% owned by the taxpayer, was hit by restructuring costs of £453 million and £856 million in "litigation and conduct" charges.

Adjusted operating profit, excluding one-off charges, was up 16% to £1.63 billion as the bank benefited from "generally benign credit conditions".

The loss attributable to shareholders of £446 million compares to a profit of £1.2 billion for the same period a year ago.

RBS said the hit for litigation and conduct charges related to "foreign exchange and mortgage-backed securities litigation in the United States together with other customer redress".

Within this was a £334 million charge for forex investigations and litigation and £100 million set aside to cover compensation for mis-sold payment protection insurance (PPI).

RBS has already paid out £399 million in penalties to US and UK regulators over the forex scandal.

Today's restructuring costs mainly related to a write-down in the value of US premises.

The results come after RBS in February reported an annual loss of £3.5 billion.