LONDON (Reuters) ? UK insurance brokers could at last be forced to come clean if they won?t volunteer how much they are paid and by whom, nearly two years after the New York Attorney General Eliot Spitzer?s probe into brokers? revenues.

The way insurance brokers are paid remains shrouded in mystery, despite the revelations of bid-rigging and illicit payments from insurers uncovered by the Spitzer probe.

Brokers still routinely accept controversial ?contingent commissions? from insurers, even though Spitzer forced the big three US brokers, Marsh, Aon and Willis to drop them, saying they acted as inducements for brokers to steer business to certain insurers.

?We have a two-tier market in the UK, where some brokers are taking more profit and contingent commissions than they were pre-Spitzer,? said Toby Foster, Head of UK Retail at Marsh.

The problem is that although Spitzer effectively made the big brokers sign up to stringent disclosure rules and drop payments from insurers, industry regulators have held back from formally forcing other brokers to do likewise.

But that may soon change in the UK. A simmering feud over fees between underwriters and brokers in London has boiled over into a public row, which could see the regulator finally act if the brokers won?t.

A group representing Lloyd?s underwriters, the Lloyd?s Market Association (LMA), called on the watchdog, the Financial Services Authority, to break the impasse created by brokers dragging their feet over disclosure.

Many brokers have ignored a compromise agreement hammered out after over a year of hard bargaining between the LMA and an influential broker body that intermediaries should voluntarily reveal on policy documents what they are earning.

Currently, brokers may receive two, or even three, different fees relating to a single client or piece of business, without the knowledge of either the clients or insurers, the LMA said.

?There?s quite a strong feeling among underwriters that our competitiveness has been damaged because the brokers have their hands in the cookie jar. Hence the feeling they should be more transparent,? said the chief executive of a London insurer.

The Financial Services Authority has so far held off from intervening, saying it preferred the market to reach its own agreement.

But the power of brokers is so immense, neither insurers or buyers have the power to compel them to change their ways.

All the London market?s premium income of around ?150 billion ($279.9 billion) comes from brokers.

FSA chief executive John Tiner has said big insurance buyers need to ?pull their weight? in making brokers more transparent.

But a campaign to make brokers disclose their earnings failed to make headway because of a lack of cooperation from most brokers, said David Gamble, executive director of AIRMIC, which represents many insurance buyers at FTSE 100 firms.

It took the Spitzer probe to make them open up their books to their clients, he said.

Now, big insurance buyers get virtually all the information they need on brokers? earnings, but Gamble suspects mid-sized companies may still be oblivious to how much their middlemen make.

?That?s where I support the LMA, because I don?t think the market has moved far enough,? said Gamble.

A survey of 500 mid-to-large UK companies conducted by London insurers earlier this year revealed a large degree of ignorance among insurance buyers over how ? and how much ? their brokers are paid.

Only one in five respondents was aware that brokers earn commission over and above what they charge clients, while buyers underestimated the total level of commission brokers make.

They guessed an average of 9.7 percent, when in reality brokers typically make between 17.5 and 20 percent.

When asked again last week what the FSA?s position is on disclosure, Tiner hinted at a growing impatience with brokers.

?A year ago I was saying we?re not going to (intervene). I?m now saying that if, when we review this in the autumn, the market hasn?t been able to respond, then we may need to intervene,? Tiner said.

?In my view it would be regrettable if disclosure to clients had to be mandated, because I think the brokers should reach that decision themselves. We shouldn?t have to be regulated into it,? said Marsh?s Foster.

If the brokers won?t listen to the buyers, they will have to listen to the regulator, he said.