Brown, the former Romney protege and senator from Massachusetts, said it was inappropriate for Romney to call Trump a phony and flip-flopper.
"You know, I have a very strong relationship with the governor," Brown told Boston Herald Radio's "Morning Meeting" on Thursday. "He's certainly has the ability and the right as somebody who has been there and won elections and fought in major elections to say whatever he wants. I just happen to disagree with him, and if he and other folks in the establishment want to do something about Donald Trump they should have probably done it months ago."
Brown said Romney's speech was not his style and made him feel uncomfortable.
"To do it now that he's in the lead, it just looks like unfortunately, you know, they're kind of ... it doesn't look good. It didn't make me feel comfortable listening to him because that's not his style," the former senator said.
And, said Brown, for Romney to call Trump a phony flip-flopper was inappropriate.
"It got a little personal," he said. "Obviously I don't mind drawing contrast at all, but to call people phony and fake and that sort of thing I think is inappropriate, certainly. That being said, I'm gonna continue to support him. I think what he has done, the governor, is he is going to rally even more people to come out for Donald Trump and mobilize them even more and have them understand what's at stake here."