New rules allowing painkillers like bute to be used on horses during competition will not come into force until next April.

The International Equestrian Federation (FEI) has backtracked on the plans following worldwide uproar over the new rules, due to come into force on 1 January 2010.

Instead, the new Equine Prohibited Substance List and the accompanying regulations — which allow bute, aspirin and flunixin, along with several other equine drugs to be used in competition — will come in on 5 April 2010.

Announcing the delay this afternoon, FEI president Princess Haya said: “The FEI has been criticised for not providing sufficient time for consultation…and there has been widespread unease about the late publication of the progressive list.”

The FEI says the intervening months will be used for “broader debate and consultation” and “supplementary research“.

Princess Haya added: “Views that have been expressed are being taken extremely seriously by the FEI as legitimate welfare concerns and we give similar importance to our membership’s decision to effect a policy change.”

On 19 November, the FEI general assembly voted 53-48 for the change in policy in Copenhagen.