Former Olympic champion Daley Thompson knows how difficult it is for athletes to make themselves available for drugs testing, but believes Mo Farah was "cutting it so fine" by missing two tests.
Farah on Friday issued a statement denying he had ever taken performance-enhancing drugs after reports emerged claiming he missed two drugs tests prior to the London 2012 Olympics, at which he won gold in the 10,000 and 5,000 metres.
Those claims also came soon after a TV documentary alleged that Farah's coach Alberto Salazar had been involved in doping - which the American has denied.
Former decathlete Thompson, who won gold at both the 1980 and 1984 Games in Moscow and Los Angeles respectively, said in the Daily Mail: "Who misses two drugs tests? Two?
"I know it must be a real pain to have to give your whereabouts for an hour every day, but it's your job. It's simple. It's your life, your career, your income - everything. They are the rules and you have to follow them.
"You can maybe just about understand missing one test, but two? You are cutting it so fine. You might be in an accident or your flight is delayed the next time the testers come calling and then you are toast."
Over his career, Thompson claimed a medal haul including four world records, the two Olympic gold medals, three Commonwealth titles and wins in the World and European Championships.
The 56-year-old added: "The testing procedure has become a lot more sophisticated since I was competing, but I still had to be available for out-of-competition tests when required.
"I didn't have to give an hour a day, every day, like the athletes do now but you had to make yourself available within a certain time frame and let the authorities know where you were living or staying.
"I found it so intrusive having someone watch you give a urine sample but it was part of my job. I remember sitting for three and a half hours, waiting until I could produce a sample, after I won Olympic gold in Moscow in 1980 and then I had nobody to talk to on the way home, but you just got on with it."
Thompson is hoping for Farah's sake that the allegations against Salazar are proved wrong as the 32-year-old stands by his coach.
He added: "His career could be damaged in the long term. But until I know the facts I will continue to want to see the best in everybody - including Mo, who has denied ever taking performance-enhancing drugs.
"We are desperate for Mo to be clean. It's not as damaging for the sport as if it was Usain Bolt missing tests but Farah is a big name in the sport and certainly in this country."