LONDON, May 31 Reuters Markets participants have a month to stop using Libor, the tarnished interest rate banks were fined for trying to rig, Britain39;s Financial Conduct Authority FCA said on Wednesday.

The London Interbank Offered Rate Libor reflected the cost of lending between banks, using quotes from panels of banks in 35 variants across five currencies.

Most have already been scrapped and remaining dollar quotes end on June 30, replaced by risk free rates compiled by central banks like the Federal Reserve in the biggest switch in markets for decades, raising concerns about pricing bank assets during market shocks.

This is the last remaining Libor panel and its end marks another critical milestone in the transition away from LIBOR, the FCA said in its final messages on the rate.

It was once dubbed the world39;s most important number due to wide use in pricing mortgages, derivatives, credit cards and student loans.

Firms must continue to actively transition contracts that reference Libor to appropriate, robust reference rates, and we continue to expect firms to deliver demonstrable progress, the FCA said.

Market participants were given permission to continue using dollar Libor in new contracts on a limited basis, but the FCA said on Wednesday this would end on July 1.

The 1, 3 and 6month dollar Libor rates only will be published in a synthetic form for legacy contracts from July 3 to endSeptember 2024.

Synthetic Libor settings will not continue simply…