A CRIMINAL investigation into former traders at Royal Bank of Scotland over the Libor interest rate-rigging scandal is expected to drag into next year.

The UK Serious Fraud Office is understood to have written to the financial regulator to ask it to put off the publication of civil findings against at least two RBS traders.

It is believed this indicates the SFO is still pondering whether to charge individuals involved. Any Financial Conduct Authority disclosure may be considered improper if there was to be a jury trial.

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It is understood that in at least one case the SFO has said it might not decide on whether charges will be made until next March.

The Edinburgh-based bank, which is 81 per cent-owned by the taxpayer, was hit with £390 million in penalties for its role in the manipulation of Libor - the benchmark rate some of the world's leading banks charge each other for short-term loans - amid a series of hefty fines levied on banking giants.

In 2012 the bank sacked four traders over their alleged involvement in the scandal.

RBS is one of a number of banks being investigated.

Allegations about an interconnected web of financial firms involved in rigging Libor were raised when Tom Hayes, a former trader at investment banks Citigroup and UBS, was charged in June 2013 with conspiring to fix key interest rates with employees at eight other financial firms.

Hayes, the first person to be charged by the SFO with Libor-rigging offences, is alleged to have variously conspired with Royal Bank of Scotland, JP Morgan Chase, Deutsche Bank, Rabo­bank, RP Martin, HSBC and Tullett Prebon to manipulate the rate. He is also alleged to have conspired with colleagues while working for UBS and Citigroup.

He denies the charges.