Updated

Sen. Scott Brown has infuriated women’s groups by poking fun at rival Elizabeth Warren’s physical appearance in response to her put-down of his nude photo shoot when he was a law student, yet he also is being defended by two female Republican senators.

The controversy started Tuesday, when Warren, a Harvard professor and consumer activist, took a shot at Brown during a debate. She and five other Democratic candidates seeking to oust Brown from the seat once held by Ted Kennedy were asked how they paid for their college educations.

The questioner noted that while Brown was in law school, he posed nude for Cosmopolitan in a photo spread. Warren began her response by saying, “I kept my clothes on.”

“Thank God,” Brown replied with a laugh during a radio interview Thursday.

One group, the National Organization for Women, went as far as to suggest that Brown should not run for re-election – a suggestion that the female GOP senators batted down.

“Scott was merely responding to comments made by professor Warren in which she made light of the difficult choices in his life,” Sen. Susan Collins, R-Maine, said in a statement.

“It’s wrong to mock anyone who had to make hard choices to overcome tough obstacles,” she added. “His story is no different than millions of Americans who are doing everything they can to make ends meet.”

Sen. Kelly Ayotte, R-N.H., said, “I know Scott Brown’s story, and I know that he had many obstacles to overcome in his youth. It’s inappropriate to make light of his personal circumstances, or to disparage or belittle him for the decisions he made to improve his life. Scott is one of the best guys to work with in the Senate, and I am proud to call him my colleague.”

Brown also defended his decision to pose for the magazine, saying modeling was his best option to pay for school.

“I didn’t go to Harvard, I went to the school of hard knocks and I did whatever I had to do to pay for school,” he said.

Brown attended two private universities -- Tufts University and Boston College Law School. Warren attended two public schools -- the University of Houston and Rutgers University, where she earned a law degree.

Warren brushed off Brown’s comment on Thursday afternoon.

“I’ll survive a few jabs from Scott Brown over my appearance,” she said. She also denied trying to take a shot at him during the debate.

“I answered a question about how I paid for college,” she said. “I worked a lot of part-time jobs and actually one full-time job.”

The Massachusetts Democratic Party immediately pounced on Brown’s comments.

“Sen. Brown’s comments are the kind of thing you would expect to hear in a frat house, not a race for U.S. Senate,” said Clare Kelly, executive director of the state party. “Scott Brown’s comments send a terrible message that even accomplished women who are held in the highest esteem can be laughingly dismissed based on their looks.

Terry O’Neill, president of the National Organization for Women, decried Brown’s comment to Politico as “the kind of sexist misogynistic attack that we have very sadly come to expect from politicians whenever there is a strong woman who is capable and really dedicated to the betterment of all people.”

She added that Brown’s remark is reason for him to “reconsider whether he should be a United States senator,” and “he should seriously consider dropping out of the race.”

The Associated Press contributed to this report.