Sen. Scott Brown (R-Mass.) on Friday urged Mitt Romney to release his tax returns.

"He’s in a category, a lot of those folks are in categories that we don’t really understand," Brown said on 96.9 FM on Friday, according to the Boston Herald. "And certainly he has to release his returns. I understand he’s going to do that like everybody else when they become ready and available in April."

Romney has repeatedly been asked when he planned to release his tax returns. Critics on the right and left have suggested Romney is avoiding releasing his returns because he has something to hide.

On Friday, Romney told radio host Laura Ingraham that he didn't think he should release his tax returns just because his father, Michigan Gov. George Romney (R) started the tradition of releasing tax returns prior to his 1968 presidential campaign.

"We talked about that beforehand, and what he did in 1967 is very different than what is going to happen today," Romney said Friday. "The idea that I am supposed to follow exactly what my dad did is not something I find terribly compelling — we disagreed in the past. … I admire my dad, but we don’t do things in exactly the same way."