An expected wave of fines and sanctions on a group of banks – including Royal Bank of Scotland and Barclays – for rigging foreign exchange markets is thought to have been delayed until next week.

Barclays and the bailed-out bank RBS are part of ongoing discussions with the US Department of Justice over the way the £3.5tn-a-day currency markets have been manipulated. Swiss bank UBS and US bankers JP Morgan Chase and Citigroup are also involved in the long-running talks to reach a settlement that could atotal more than $5bn.

According to Bloomberg, the DoJ is attempting to secure guilty pleas from the parent companies of the banks, rather than just their subsidiaries, over competition breaches. Last year, BNP Paribas pleaded guilty to violating US sanctions towards Sudan and Cuba.

The investigation by the DoJ is part of a global investigation into the way the foreign exchange markets have been manipulated by major banks and follows £2.6bn of fines imposed by other US regulators and the UK Financial Conduct Authority in November.

Barclays is yet to be fined by the FCA and pulled out of that global settlement in November. It has set aside £2bn in anticipation of regulatory action and said in April it was “working hard to expedite” the matter.