Ramona Singer isn't a fan of LuAnn de Lesseps' relationship.

During a new interview, the Real Housewives of New York City star slams de Lesseps' fiance, Thomas D'Agostino Jr., for hiding their past relationship from de Lesseps.

“I don’t think relationships should be built on lies,” Singer told Radar Online on Wednesday. “He said him and I went out once or twice. Why? We went out a dozen times! Why be deceitful?”

D’Agostino Jr. reportedly "bent the truth" about his past romance with Sonja Morgan.

“LuAnn, he knew was living with Sonja and he never told her that they were lovers,” Singer revealed. “Why would he not disclose he was with Sonja repeatedly? Who cares!”

Singer went on to reveal that her co-star, de Lesseps, should have come to her when her romance with D'Agostino began rather than let her discover the news elsewhere.

“With Luann, of course she can date whomever she wants,” Singer continued. “I thought we were developing a true friendship. I was disappointed. She should’ve said, ‘The guy you were dating, I am now.’ Just giving the heads up, not permission, the courtesy!”

And as for D'Agostino, Singer found it to be quite odd that he would have asked her out after first dating her longtime friend, Sonja Morgan.

“I find it very strange that he would ask me on dates knowing I’m so close to Sonja and that they were lovers,” she confessed.

Singer and her husband, Mario, parted ways years ago due to his affair with a New York City socialite and ever since, Singer has been enjoying life as a single woman in the Big Apple.

For more of Ramona Singer and her co-stars, tune into The Real Housewives of New York City airing on Wednesday nights at 9 p.m. on Bravo and check out a sneak peek of tonight's new episode below.