Dettori tested positive for a banned substance at Longchamp in France on September 16.
He is now likely to face a worldwide ban from the sport for up to six months, but Francome, who is a close friend of Dettori, has no sympathy for the Italian.
"I think the world of him. But the bottom line is this, drugs have no place in sport," said Francome. "They have no place in life, in my book. The only thing snorting in a paddock ought to be a racehorse.
"And no matter what the rights and wrongs of Frankie's case, he's old enough to know better than to get himself involved with this sort of nonsense. He is racing's greatest ambassador. He is an ebullient character who lights up a room when he walks into it.
"What damage has he done to himself and the sport if these allegations contain the slightest grain of truth? He has five lovely kids and a smashing wife. What must they be thinking this morning? I appreciate he was in Paris, but he doesn't have to behave like he's riding in the Tour de France."
If Dettori were to be banned for six months, he would miss the 1000 Guineas, 2000 Guineas, The Oaks and The Derby.