The City regulator looks set to impose penalties totalling more than £1 billion on banks caught up in the foreign exchange - forex - market-rigging scandal.

Six firms are said to have been in talks with the Financial Conduct Authority to reach a settlement, by the end of this month, over the alleged misconduct.

Reports suggest the FCA could publish its ruling on Wednesday, with each bank facing a penalty of between £225 million and £250 million, a total of around £1.4 billion.

This would dwarf the £532 million in penalties imposed by the regulator on banks and City brokers over the previous big regulatory scandal involving the manipulation of the interbank lending rate, Libor.

The banks are also likely to face penalties from US regulators. In the past these have been much larger than those imposed in the UK.

Fines by global authorities over Libor have totalled billions of pounds. But FCA chief executive Martin Wheatley has said the forex allegations are "every bit as bad".

The six banks reported to have been in talks with the regulator over a settlement are HSBC, Barclays, Royal Bank of Scotland, Citigroup, JP Morgan Chase and UBS.

The expected record fine over the forex scandal will add to the large sums the FCA has collected over Libor.

Much of the money has been allocated to charities.