The changes mean it is prohibited to administer anabolic steroids, and that any horse that tests positive for the banned drugs faces a racing ban of 14 months.
This zero-tolerance approach goes further than the new worldwide standards issued in October and the British Horseracing Authority (BHA) said it would help combat one of its “biggest threats”.
It comes after former Godolphin trainer Al Zarooni and Newmarket-based Butler were banned for eight and five years respectively last year after horses in their care tested positive for steroids.
“The enhanced, zero-tolerance policy, which exceeds the international minimum standard, has the objective of ensuring that British racing remains at the forefront of tackling an issue that ranks amongst the biggest threats faced by any world sport,” said BHA chief Paul Bittar.
“After a challenging 16 months, as a result of the actions taken already by several nations, the sport globally is now in a much better place when it comes to the regulation of anabolic steroids.”