Royal Bank of Scotland has escaped €115m of fines for alerting the European commission’s competition watchdog to two attempts to fix the prices of key interest rates.

RBS, which is 81%-owned by the taxpaer, was fined £390m last year for manipulating Libor by regulators in the US and the UK. It was given immunity from one €110m fine after telling the commission it had tried to influence Swiss franc interest rates with JP Morgan. The Wall Street bank was fined €61.7m – getting a 40% discount for co-operating with the investigation into Swiss franc Libor-rigging between March 2008 and July 2009.

In a separate action, RBS was also spared a €5m fine for another offence – again involving the pricing of a Swiss franc interest rate – after alerting the commission to the actions of JP Morgan, and Swiss banks UBS and Credit Suisse which were fined a total of €32m.

Issuing the findings against JP Morgan and RBS for rigging Swiss franc Libor, Joaquín Almunia, the commission’s vice-president in charge of competition policy, said it was third time Europe’s competition authorities had fined banks and brokers for forming cartels to fix crucial benchmark interest rates such as Libor or Euribor.

In December 2013 it hit six firms, including RBS, with combined fines of €1.7bn for colluding to fix Euribor and yen Libor. The latest run-in with regulators came as the body which controls the taxpayer’s stake in RBS said dealing with the mistakes of the past could delay any attempt to sell off part of the government’s shareholding. Even so, UKFI said it had meetings with its adviser JP Morgan five times in the past month to discuss a potential sell-off and there was more interest from potential buyers of the shares, bought for £45bn in 2008 and 2009.

The taxpayer stake is worth about £32bn and James Leigh-Pemberton, UKFI’s chairman, said if the current business model for RBS continued to show results then “we can accelerate the path on which we get back to the private sector”. He gave no indication when this might occur.

Leigh-Pemberton also admitted that the Treasury had ruled out allowing RBS to pay higher bonuses in April to avoid a “major public controversy”.

UKFI had thought RBS should be allowed to ask shareholders to back plans to pay bonuses twice the size of salaries but the Treasury had ordered payouts remain no higher than salaries, in line with the EU’s cap on bonuses.

Andrew Tyrie, the Conservative MP who chairs the Treasury select committee, said UKFI had a “thankless task” and should be wound up and put back inside the Treasury.