Global benchmark interest rates should be based on actual transactions rather than estimates, the top global securities regulatory body said on Tuesday, after a spate of rate-rigging scandals knocked confidence in the system.

Financial industry benchmarks have come under intense scrutiny since a rigging scandal erupted last year over LIBOR, a global benchmark rate at which banks lend to each other that influences in turn how much businesses have to pay for loans.

The International Organization of Securities Commissions (IOSCO) wants more effective whistle blowing mechanisms, a code of conduct for individuals who submit figures for benchmarks and stronger policing of institutions that compile rates.

Last year UBS paid a fine of $1.5 billion for manipulating LIBOR and euro yen contracts and Barclays paid $450 million for false fixing of LIBOR. At least a dozen other banks are under investigation for rate rigging.

National and regional watchdogs are investigating a wide variety of benchmarks in the wake of the LIBOR scandal and a similar row over Euribor—the Euro Interbank Offered Rate.

The top U.S. derivative regulator is also investigating a widely used benchmark for swaps—ISDAfix.

The European Commission plans to present a draft law in the coming months that is expected to oblige key banks to belong to panels that submit data used to set major benchmarks like LIBOR.

“To promote market integrity, it is critical that benchmark interest rates be anchored in observable transactions and supported by appropriate governance structures,” said Gary Gensler, the Chairman of the U.S. Commodity Futures Trading Commission, who is jointly leading IOSCO’s task force on benchmarks with Martin Wheatley, Britain’s top UK regulator.

IOSCO sets standards for securities regulators worldwide.

“I support that international regulators and market participants have begun to discuss appropriate alternatives and possible approaches to a smooth and orderly transition from LIBOR, Euribor and similar rates,” Gensler added.

IOSCO said it was opening a consultation period on its proposals, due to close on May 16, after it received more than 50 comments earlier this year in a first round of feedback from investor associations, brokers, authorities such as the European Central Bank and other entities.

In the UK, the newly-renamed Financial Conduct Authority (FCA) will send a letter to a group of about 40 banks and brokers over the next 48 hours, setting out IOSCO’s findings and how the proposed measures would impact UK institutions, a source familiar with the process told Reuters.

The firms will then be given a period of time to make submissions to the FCA, the source said, adding that it was not a formal consultation process.

The benchmarks covered by IOSCO’s review span everything from equity swaps to currency and commodities exchanges, as well as interbank rates and overnight lending.

Just some of these will be covered in the initial FCA work, but further work on other benchmarks may be done later, the source told Reuters.

The FCA declined to comment beyond a press release it issued earlier on Tuesday saying it would undertake “further work to examine any potential weaknesses in the wider range of benchmarks captured under the IOSCO Principles.”