Faced with growing calls to increase transparency in derivatives, the incoming head of the U.K. Financial Services Authority warns that such is easier said than done.

The Association for British Insurers joined a growing chorus of trade groups in Britain calling for increased disclosure regarding contracts for difference. The ABI warned that the derivatives make tracking ownership—especially hedge fund ownership—difficult. But Hector Sants, who tomorrow takes over as head of the FSA, warns that a new system of ownership disclosure designed to reflect economic interest, rather than voting rights, is a complicated affair.

“It is an easy statement to make, but very difficult to implement,” he said. The current head of wholesale and institutional markets at the FSA, Sants said of the Takeover Panel’s requirement that CFDs be disclosed during offer periods, “It is not immediately obvious to us that this is scalable.” He said any alteration in policy was unlikely before next year.

Sants was named the new CEO of the FSA last week.