UK Sport has said it does not fund research projects aimed at giving athletes a performance advantage at the expense of their health, after the Mail on Sunday reported that it backed an experimental nutritional programme at the 2012 London Olympics.
The newspaper said it had seen documents that showed as many as 91 elite athletes across eight Olympic sports were given an energy-boosting drink called DeltaG as part of the project, which cost hundreds of thousands of pounds of public money.
It said the substance, a synthetic version of a naturally occurring body acid called ketones, was then in the first stage of in-competition testing in humans.
The report said 40% of athletes experienced side-effects including vomiting and gastrointestinal upsets.
"UK Sport resolutely refutes any accusation that Olympians were used as 'guinea pigs', and finds this allegation both misleading and offensive," the organisation said in a statement.
"By its very nature, any performance innovation project is at the cutting edge of science and emerging technology, as any advantage for Great Britain is only possible before it is widely available -- as was the case for the ketone tester which became commercially available in 2018.
"UK Sport is fully committed to developing a high performance culture that is truly inspirational and one that will set us apart from our global competitors -- but UK Sport will never seek to win medals at any cost."
UK Sport said the project had received independent ethical approval from the Research Advisory Group in January, 2012.
"Additionally, UK Anti-Doping confirmed in writing, after seeking clarification from the World Anti-Doping Agency, that WADA had 'no reason to consider such substances as banned under the 2011 List of Prohibited Substances and Methods'," it added.
British athletes won 29 gold medals at the 2012 Olympics.