Scotland's Crown Office & Procurator Fiscal Service has decided against bringing criminal proceedings against the Royal Bank of Scotland or any of its directors or managers, relating to the rights issue of shares in April-June 2008, months before the bank collapsed and had to be bailed out by the UK Government.

Investors lost about 90% of the value they put into the bank at that time. An investigation by the Financial Services Agency (now the Financial Conduct Authority), including into questions of possible dishonesty, which resulted in a report published in 2011, however concluded that despite "numerous poor decisions and imperfect processes", there was insufficient evidence to bring enforcement actions against individuals responsible which had a reasonable chance of success in tribunal or court proceedings.

In view of the public concern, the Crown undertook its own independent investigation following publication of that report, which focused on the rights issue and involved "detailed consideration" of whether there was any evidence of criminal conduct associated with that.

An updating statement issued today by Crown Office reported that: "If there were such evidence those responsible would face prosecution. If not, the public in Scotland could be reassured that the matter had been properly investigated.

“This was an extremely complex investigation which included the examination of over 160,000 documents by a team of specialist forensic accountants and banking experts, supervised by the Serious & Organised Crime Division.

“The investigation involved close co-operation with a range of financial regulators and banking institutions, including the Financial Conduct Authority, the Prudential Regulation Authority, the Federal Reserve Bank of New York, the Serious Fraud Office and the Financial Reporting Council.

“Following careful examination of all the evidence seen to date, Crown counsel have decided that there is insufficient evidence in law of criminal conduct either in relation to RBS as an institution or any directors or other senior management involved in the rights issue."

The statement added: “If any further evidence comes to light which is relevant to this enquiry it will be considered by the Crown and we reserve the right to make further enquiry, if considered appropriate.”

Civil litigation class actions against the bank by disappointed investors are continuing.