Sydney - The World Medical Association (WMA) on Sunday urged doctors not to enforce controversial new IAAF gender rules for classifying female athletes, warning that attempts to do so would breach ethical codes.

READ: Caster: How medication will impact her performance

It follows South African runner Caster Semenya last week losing her court challenge against the International Association of Athletic Federations (IAAF) over plans to force some women to regulate their testosterone levels.

The decision by the Court of Arbitration for Sport (CAS) means that female athletes with elevated testosterone will have to take suppressive treatment if they wish to compete as women in certain events.

The IAAF argued that athletes like the two-time Olympic champion had an unfair advantage over others.

But World Medical Association chairman Frank Ulrich Montgomery advised doctors to play no part in enforcing the rules during an interview with the Australian Broadcasting Corporation.

"We do think it is extremely serious if international sports regulations demand physicians to prescribe medication - hormonally active medication - for athletes in order to reduce normal conditions in their body," he said.

In a 2-1 decision, CAS judges dismissed Semenya's appeal against the measures targeting "hyperandrogenic" athletes - or those with "differences of sexual development" (DSD).

They said that although the rules were "discriminatory ... such discrimination is a necessary, reasonable and proportionate means of achieving the IAAF's aim of preserving the integrity of female athletics in the Restricted Events".

Montgomery said that for women with DSD "it is just normal to be androgenic and there is nothing pathological about the situation of this athlete".

"No physician can be forced to administer these drugs, and we definitely urge our colleagues to refrain from giving hormonally active medication to athletes simply because some regulations demand it," he added.

"If physicians do apply these drugs they do break ethical codes.

"The basic ethical code of all medical practice is never do harm, and it is doing harm to a perfectly normal body with just a rather high level of testosterone by administering drugs to use this in order to make them eligible for women's sport under these regulations."

The DSD rules - first adopted last year but suspended pending the legal battle - are due to come into effect on May 8. Semenya is mulling an appeal.

Montgomery said the argument that Semenya had an unfair advantage over others didn't make sense, using the height of some basketball players to make his point.

"The next issue would be that we demand basketball players who are taller than 2.25 metres should reduce their height surgically to something else because, of course, they do have an advantage over other basketball players that are somewhat smaller," he said.

"So where is the limit to this? And therefore we say medicine shouldn't interfere with non-pathological situations simply to enhance sports activities."