The FSA regulatory regime will be more onerous than GISC, British Insurance Brokers' Association (Biba) chief executive Mike Williams has warned.
And it must include absolutely everyone who sold general insurance, he added.
Williams urged brokers to remain with GISC, although the Treasury announced that regulation would be transferred to the FSA by 2004.
The Treasury promised that the FSA would give credit to brokers and intermediaries that were already GISC members.
Williams said: "Brokers and intermediaries will need to be in good compliance shape for the FSA regime, which will almost certainly be more onerous than GISC."
He said Biba would "take a strong and influential role" in thrashing out the new regime for brokers.