The Royal Bank of Scotland has earmarked 3 billion pounds to cover potential litigation claims related to mortgage-backed securities and other products sold before the financial crisis. The new provisions, on top of more than £4 billion in charges announced in November, are expected to drag the bank into a deep loss for 2013 when it reports results next month. Eight top executives of the bank in which the British government holds 81% stake, will not receive bonuses for 2013 as a result, the bank said. Its chief executive, Ross M. McEwan, who took the reins in October, has already said that he will not take a bonus for 2013 and 2014. The charge is the latest setback for the chief executive as he tries to change the bank’s culture and prepare it for private ownership. McEwan said billions of pounds have been spent to resolve conduct and litigation issues in recent years and costs on this scale were not predicted by anyone when R.B.S. was rescued in 2008. They come in addition to the costs of restructuring the bank’s bad assets and restoring its funding to prudent levels after the financial crisis, he added. The bank had earlier said it would take a £1.9 billion charge for potential claims related to mortgage-backed securities and other securities litigation in the United States. It is among the banks being investigated by the Justice Department over mortgage sales and is the subject of a lawsuit by the Federal Housing Finance Agency over mortgages sold to Fannie Mae and Freddie Mac.