Insurers that inadvertently deal with unauthorised intermediaries after 14 January will not be punished by the FSA.
The regulator has given "implied" indications that an insurer who has taken all reasonable steps to ascertain whether an intermediary is authorised will not face censure if it transpires that the intermediary is not authorised.
ABI head of market regulation Chris Hannant said: "The FSA expects insurers to do everything they can, and if they do, that will be taken into account."
The indication allays insurers' concerns over the late publication of the full list of authorised firms.
There are fears that the list may not be available until after 14 January.
Before Christmas, the Treasury helped to smooth the transition to FSA regulation by allowing late applicants who have yet to receive authorisation to continue to trade.