Pressure is mounting on the FSA to make broker commission disclosure mandatory after the Federation of Small Businesses (FSB) declared its support for full transparency.

"We would be in favour of commission disclosure," said an FSB spokesman.

"What small businesses want is a level of transparency so they can make informed choices about their insurance provider."

Small businesses, said the FSB, would benefit from full disclosure, which would bring increased competition into the market, driving down insurance costs.

"Small businesses have to manage costs," said the spokesman. "Transparency would mean that businesses would know what the hidden costs are."

The FSB said it would encourage its members to ask brokers to disclose commissions.

But the spokesperson added: "Small businesses are restricted on time, so it would be easier if brokers automatically disclosed."

The call comes after the Association of Insurance and Risk Managers (Airmic) said it had uncovered a divide in how brokers were disclosing earnings.

"We remain concerned that these benefits are available mainly to the large, knowledgeable buyers," said Airmic spokesman, Andrew Cornish.

"Smaller companies are not always receiving the same consideration from their brokers.

"There seems to be a two-tier market emerging which - if it persists - could result in much of the good work we have seen so far undone," Cornish said.