Senators said Oz - who often touts the virtues of weight-loss products on his syndicated television show - bears a large measure of responsibility for the problem. Oz countered by saying he himself was the victim of the scammers, NBC News reported.
However, Oz's claim was dismissed by Missouri Sen. Claire McCaskill, a Democrat who chairs a Senate subcommittee on consumer protection.
"I don't get why you need to say this stuff because you know it's not true," McCaskill said at the hearing, NBC News reported.
"So why, when you have this amazing megaphone, why would you cheapen your show by saying things like that?"
She accused Oz of playing a role in perpetuating diet scams.
Read: The Kardashians and the diet pills
"When you feature a product on your show it creates what has become known as the 'Dr. Oz Effect' - dramatically boosting sales and driving scam artists to pop up overnight using false and deceptive ads to sell questionable products," McCaskill said.
"While I understand that your message is occasionally focused on basics like healthy eating and exercise, I am concerned that you are melding medical advice, news, and entertainment in a way that harms consumers," she added.
Oz acknowledged that he uses "flowery" language on his shows and knows that when he recommends a diet product, scammers use his words to sell bogus products, NBC News reported.
Read: How to avoid health scams
The diet products he recommends give hope to people trying to lose weight, according to Oz.
"I actually do personally believe in the items I talk about on the show," he said. "I recognise that oftentimes they don't have the scientific muster to pass as fact. I have given my family these products."Watch: CNN clip of the Senate hearing and Dr Oz's response
The Senate hearing is a follow-up to January's Federal Trade Commission crackdown on bogus diet products, NBC News reported.
Read: What to look for in Internet diet scams
Oz has a huge impact on the marketing of such products, the FTC's Mary Koelbel Engle told the hearing.
"For instance, within weeks of an April 2012 Dr. Oz Show touting green coffee bean extract as a miracle fat burning pill that works for everyone, the marketers of the Pure Green Coffee dietary supplement took to the Internet making overblown claims - like 'lose 20 pounds in four weeks' and 'lose 20 pounds and two to four inches of belly fat in two to three months' -- for their dietary supplement," she said.
Why are we forever chasing quick-fix diets?
The dodgy ingredients in diet pills
Alcat diet scam exposed