One of Australia's leading international racing identities has resigned from the powerful Breeders' Cup board in protest at the organisation's backflip over the use of the anti-bleeding drug Lasix.

Oliver Tait, Darley's chief operating officer, stood down voluntarily following the decision to allow the drug to be used in Breeders' Cup races.

"The Breeders' Cup has reversed its previously agreed and stated position that the 2013 Breeders' Cup World Championships will be conducted without Lasix," Tait said in a statement issued by Darley.

"As a consequence, I have resigned from the board of the Breeders' Cup."

Lasix, also known as Salix, is banned as a raceday treatment in most countries but is widely used in the United States to help prevent internal bleeding.

The Breeders Cup board voted last week not expand its prohibition of Salix to all races at the meeting but opted to continue the 2012 policy of banning it in the juvenile races.

"Sheikh Mohammed, Darley's principal, has been one of the biggest players in American racing for the last 30 years," Tait said.

"His vision for the sport in America is a future where racing is enjoyed and admired by a new generation of participants and enthusiasts. A true world championship, to be enjoyed and admired by all, needs to be medication free.

"Progress is being made in all sports around the world in relation to drugs. This is not progress.

"The Breeders' Cup is a leader of this sport, and I was extremely proud to serve on its board. Having rightly and boldly chosen to lead the way on the issue of drugs in racing in 2011, it has now stepped back in time."

Tait, formerly the general manager of Darley Australia, spent two years with Darley in Kentucky before relocating to Newmarket in England.

Those against the use of Lasix believe it helps retain infirmities in the gene pool.

A major concern for racing authorities is that the drug can mask performance enhancing substances including steroids.