Britain's anti-doping chiefs have hit back after an influential group of MPs said an independent agency should take control of drugs testing in UK sport.
The Commons science and technology committee heavily criticised UK Sport, which currently runs anti-doping.
UK Sport's director of drug-free sport, John Scott, said: "The recommendation isn't backed up with evidence as to why an independent agency is required.
"My belief is firm - we are successful, and we are doing a very good job."
The committee's report, published on Thursday, said: "We are concerned at the continuation of strong perceptions within the sporting community that conflicts of interest exist.
"We find it unacceptable that suggestions for a UK equivalent of Australia's anti-doping agency Asada should be automatically dismissed without detailed review of the benefits such an organisation could offer."
What we are lacking here is real evidence
But Scott said previous reviews - by independent consultants PMP and the Department of Culture, Media and Sport - had concluded that responsibility for anti-doping should stay with UK Sport.
"The DCMS said that there was no justification for an independent body," he said.
"I'm disappointed that the report does not add much to the debate. I feel what we are lacking here is real evidence.
"Potential conflicts can be mitigated by scrutiny, and the degree of internal and external scrutiny we go through is exceptional."
Paula Radcliffe, Britain's most successful athlete of recent years, told the BBC recently: "There needs to be an independent body with no links to any funding and federations."
But Scott said: "There is a legitimate cost issue - a new organisation would be a further burden on the system.
"The Canadian anti-doping agency deals with 40% less tests than we do, but they have 38 staff. Asada has close to 50. I have 17.
"We are also one of the most reviewed anti-doping organisations in the world. To suggest that we are not under constant review is inaccurate.
"We are continuing to put in place the best anti-doping programme we can, and the effectiveness of our programme is getting better all the time."
The Commons committee also recommended that doping offenders should be hit with four-year bans from sport, rather than the current two-year penalty.
Athletics' world governing body is also keen to extend its bans, having cut them to two years in 1997 because of civil court rulings and pressure from other sports.
Scott admitted he was sympathetic to the idea, but feared it could be difficult to implement.
"That was a very hard-fought battle in the first draft of the World Anti-Doping Agency code.
"I think it comes down to the severity of the infringement. If it's a very sophisticated attempt to cheat then it's questionable whether a two year ban is enough.
"Two years doesn't necessarily mean that the athlete is excluded from an Olympic Games, and it's that threat that is the big disincentive to doping.
"But is it achievable? We've seen very strong resistance to it in several sports.
"The debate is whether it's better to have tougher penalties in some sports, or a consensus across all sports."