It has been investigating the industry since February following a series of claims that traders tried to fiddle the benchmarks.
The international body, headed by Bank of England governor Mark Carney, also wants to change the way benchmarks are calculated to reduce the chance of manipulation.
One option is to measure markets for a longer period of time, to reduce the influence of rogue traders.
Another is to adjust the way different currency trades are weighted, again influencing the daily fix published.
And the global body wants banks and brokers to implement more systems and controls to monitor traders’ behaviour, to crack down on those who thought manipulation of the indices was an easy way to boost the position of their trading books.
The investigation will conclude in November, publishing a fuller set of recommendations then.
The forex investigations are expected to join those into Libor, the interest rate benchmark which was also targeted by traders.
In addition, new Bank of England deputy governor Minouche Shafik is leading a consultation on other benchmarks, which may need more regulation.