The 2014 Wimbledon finalist from Canada, called Sharapova a cheater upon the Russian's return from a 15-month doping suspension.
Sharapova has already been slammed by other players who are unhappy that the five-time Grand Slam champion has been given wild-card entries to some tournaments.
"I don't think that's right," Bouchard, who is competing at the Istanbul Cup this week, told Turkish broadcaster TRT World. "She is a cheater and so, to me, I don't think a cheater in any sport should be allowed to play that sport again. It's so unfair to all the other players who do it the right way."
Sharapova returned to tennis on Wednesday, winning her opening match at the Porsche Grand Prix in Stuttgart, Germany. She received a wild card to play in Stuttgart, and also got them for upcoming tournaments in Madrid and Rome.
The French Open is considering an invitation for the two-time champion as well.
Some players argue that Sharapova should work her way back up the rankings by competing in lower-tier events and through qualifying for the bigger tournaments.
Bouchard went a step further, and even criticized the women's tour for allowing her back.
"I think from the WTA it sends the wrong message to young kids: 'Cheat and we will welcome you back with open arms.' I don't think that's right and definitely she is not someone I can say I look up to anymore," Bouchard said last week.
WTA CEO Steve Simon, speaking to German broadcaster ZDF over the weekend before Bouchard's comments became available, said Sharapova paid the price for using the banned substance meldonium.
"I don't think a suspension should wipe out the career's worth of work," Simon said.
After winning her second-round match in Stuttgart against Ekaterina Makarova on Thursday, Sharapova said she didn't want to react on Bouchard's remarks.
"I'm way above that. I don't need to comment on that," Sharapova said.
A day earlier, Sharapova said she doesn't feel hurt by fellow players speaking out against the conditions of her comeback.
"I can't control what people say and I never have," the Russian said. "The only thing I can control is what I do out there and those are my words. I'm always prepared to walk the walk and I have and I've done that by winning five Grand Slams and being No. 1 in the world."