The Building Societies Association (BSA) will join the ABI in lobbying the FSA over its block transfer rules.

BSA director general Adrian Coles said the rules were "a matter of concern" and that there was "a case" for banks and building societies to take action.

He said the BSA would be seeking "an explanation" from the FSA.

The block transfer rules govern the transfer of the underwriting of books of affinity business from one insurer to another.

Insurers are concerned that the requirements are anti-competitive as the rules require affinity providers to obtain the explicit permission of each one of thousands of policyholder.

The ABI is arguing that the administrative burden of contacting policyholders will mean that books of business will not move.

ABI head of market regulation Chris Hannant said the ABI had met the FSA and was "exploring options".