The bank said in its latest update that operating profits, excluding any accounting gains from debt value readjustments, came in at just £267m, down from £726m a year ago, and lower than Q2’s £818m figure.
The bank also reported it had written off Greek debt worth £142m in the three months to end of September.
Amid the crisis in Europe, RBS followed the trend set by other banks across the region as investment-banking revenue slipped 29% to £1.1bn from the previous quarter.
Overall RBS, which is 83%-owned by the UK taxpayer, said it had made a profit of £2bn after a £2.4bn uptick in the value of debt on its own balance sheet.
The bank’s chief executive Stephen Hester said the group had been “resilient” in Q3, while warning the economic recovery around the globe would take longer than anticipated.
“RBS’s third quarter results show the improved strength and resilience we have built up since 2008,” he said.
“They also highlight the external pressures facing banks, and economies more broadly, which are making the road to recovery longer and bumpier than hoped for.”
