A "betrayal", a "destruction of public faith" and a "dark day" for athletics.
Leading figures have responded to a World Anti-Doping Agency commission report, which has recommended Russia should be banned from competition.
British sports minister Tracey Crouch called the findings an "extraordinarily dark day for athletics".
The report examines claims of doping, cover-ups, and extortion in Russian athletics, which also implicated the IAAF, the sport's world governing body.
The report also states the London 2012 Olympics were "sabotaged" by participation of Russian athletes under suspicion, while Dick Pound - head of the independent commission - described it as "state-sponsored doping".
Athletics' darkest day?
IAAF president Lord Coe described the scale and depth of the report's findings "truly shocking".
After promising to "move quickly" on the independent commission's recommendations, Coe told BBC Sport: "I want to see a sport that is responsible and transparent and accountable and I will do anything it takes to achieve that. But this will not be swift road, this will be tough."
Tessa Jowell, former Olympics minister, added: "This is what destroys public faith in the competition they see on their televisions or go to see. There is very clear a problem of culture."
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What the athletes say
Paula Radcliffe, marathon world record holder, on Twitter: "Just got off plane to catch up on these damning and serious revelations. Too much to address in tweets: bottom line - truth eventually comes.
"Suspected some of this for years but way worse than imagined. Athletics needs to take strong action and move quickly forward in right direction."
Louise Hazel, British heptathlete: "I am disappointed but I am not surprised that doping continues to be rife through the world of athletics.
"I have been in situations where I have seen athletes doping right before my eyes.
"Giving athletes a two-year ban and allowing them to come back to compete for gold medals is just not good enough. Full-time bans and you are out of the sport. Simple as that."
Mara Yamauchi, second fastest British female marathon runner of all time: "I'm not very surprised, it helps to explain a lot of the suspicions I've had about particularly Russian athletes who I used to compete against.
"It's easy to direct your anger at the athletes but actually what this story really shows is that the serious wrongdoing is going on further up the chain on the part of agents, coaches, officials, directors of anti-doping and national federations and it's really those people that should be punished."
Official bodies react to Wada findings
Wada president Sir Craig Reedie told BBC Radio 5 live: "I think it's appalling and is probably worse than anyone imagined. Clearly there has been deliberate cheating and also oversight.
"While it is unpleasant that it has become worldwide debate, I think there should be credit given to my agency for having the courage to appoint an independent commission and putting it in the public domain."
International Olympics Committee statement: "This is a deeply shocking report and very saddening for the world of sport.
"The protection of the clean athletes is a top priority for the International Olympic Committee. We support the attempt of the independent commission to bring all the facts to light in the interest of the integrity of the sport and the protection of the clean athletes."
UK Anti-Doping statement: "The Independent Commission's findings highlight that the international playing field has not been level for our clean British athletes competing on the global stage. Today's findings will go some way to levelling that playing field for our athletes, and the whistle-blowers and media should be applauded for bringing these issues to Wada's attention."
BBC 5 live Track & Field special - Including former athletes Steve Cram, Paula Radcliffe and Darren Campbell examining the independent report on claims of corruption and cover-ups in world athletics.