Abbott came under fire after praising the female conservative colleague while campaigning in western Sydney yesterday, renewing debate over misogyny in Australia which raged during former leader Julia Gillard's time in office.
Rudd, who ousted Gillard as Labor leader in June, condemned the remarks.
"If any male employer stood up in a workplace anywhere in Australia and pointing to a female staff member, said, 'This person is a good staff member because they've got sex appeal', I think people would scratch their heads at least and I think the employer would be finding themselves in serious strife," he told reporters.
Ex-trainee priest Abbott defended his blunder -- the latest in a series of gaffes he has made about women -- describing it today as a "dad moment, a daggy moment maybe". Daggy is an Australian term for uncool, or not trendy.
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Yesterday, Abbott, the frontrunner to become prime minister in the September 7 polls, was asked about similarities between candidate Fiona Scott and her female predecessor in the western Sydney seat.
His finance spokesman, Joe Hockey, rose to Abbott's defence, saying the conservative leader did not mean any offence and was known for these kind of remarks.
"Tony says it to me often that I'm a sexy guy. We've got a special kind of love going," Hockey told commercial television, adding that Abbott had described him as the "parliamentary George Clooney" to his colleagues.
"As long as it's not offensive, I think we shouldn't be afraid to say what we think."
Labor has consistently accused Abbott of sexism and Finance Minister Penny Wong, the most senior woman in the government, said she was unsurprised by his latest remarks.
"This is consistent with some of the views Mr Abbott has expressed over many, many years," she said.
Abbott's sex appeal blunder followed a gaffe on Monday in which he said no one person was the "suppository of all wisdom" -- a mistaken reference to drug delivery through the rectum.