Oscar became the latest player to be shown a yellow card for diving in a series of high-profile offences which prompted FIFA president Sepp Blatter to talk of the use of sin-bins.
Mourinho reprimanded Oscar following the Brazilian's tumble over Southampton goalkeeper Kelvin Davis, but insists it was a one-off.
"It's impossible for him to get a reputation, unless somebody wants to be unfair and to clean the image of other people by using Oscar's situation in the last game," he said.
"I want to make it clear: there are many divers in the world of football. There are many divers in some big clubs in the world of football.
"There are some divers in England. Not many, some. In Chelsea, no divers, no divers at all.
"Oscar made a mistake, which he tells me and I believe him, he was completely convinced the goalkeeper was coming to smash him.
"The goalkeeper didn't, he made his mistake, he was punished with a yellow card, he accept the yellow card in a very calm way.
"His manager comes after in the press to say 'well done Mr Atkinson'. End of story. Here we don't have divers."
Mourinho also stated Eden Hazard is not awarded free-kicks and penalties when he is fouled.
"It looks like opponents who can do anything to him and nothing happens," he said.
"With Hazard it doesn't matter in the box, outside the box. Not against Southampton, but week after week in the box there are penalties.
"And, as it happened in Southampton, outside the box every action is a foul and this kid is anything but a diver."
Mourinho wants diving to be eradicated from the global game.
"If Mr Blatter wants to analyse the situation, I give him my advice and my experience, because I've worked in many different countries," he added.
"Go to other countries, fight the problem in other countries, don't be afraid to go to the big clubs. Don't be afraid to go to some big players.
"And after that come to England, because in England the job is easy. England is the best country."