The fine will pale in value against the massive payments to be made to US institutions.

US regulators will receive most of the money to be paid by five major banks - Barclays, RBS, Citigroup, JP Morgan and UBS - as punishment for their involvement in the Forex scandal revealed in 2013, which saw collusion to rig foreign currency rates.

The FCA’s largest issued fine to date is £234 million, paid out by UBS in a settlement with the FCA last November.

Barclays was the only one of the five banks involved in currency rigging which did not settle with the FCA in November.

The bank was reportedly unable to settle as it could not agree a deal with the Department of Financial Services in New York, which was not investigating the others.

The failure to settle means Barclays has waved the 30 per cent early settlement discount offered to the other banks, whose combined fines totalled £1.1 billion. The Telegraph reports that Barclays could be fined as much as £250 million.

The five banks are expected to pay up as much as £4 billion in total combined fines to the FCA and US regulators. The exact value of the fines will be revealed on Wednesday afternoon.

The fines were expected to be announced last Wednesday, but the settlement was delayed by last-minute legal wrangling.