A GOP congressman has defended the "nasty woman" comment Donald Trump made during the last US presidential debate.

Texas Republican Brian Babin made the comments on the Alan Comes Show, when the host asked him if he believed Trump's insult had been appropriate.

"You know what, she's saying some nasty things," The Hill reported Babin saying.

"I think sometimes a lady needs to be told when she's being nasty. My assessment is that Mrs. Clinton has got so much baggage ... I think she's done some nasty things."

Trump made the "nasty woman" comment in response to Hillary Clinton's dig during the debate, when she said: "My social security payroll contribution will go up, as will Donald's, assuming he can't figure out how to get out of it."

Trump's insult immediately sparked the hashtag #nastywoman, with many politicians, celebrities and people around the country adding their views online, and women reclaiming the insult as their own.

Despite the outpouring of #nastywoman tweets online, that was not in fact, the debate comment that prompted the most headlines.

Trump's suggestion that he may not accept the result of the election led to an even bigger backlash, much of which came from within the Republican Party itself.

Senator John McCain, who revoked his support for Trump after footage emerged of him making lewd comments about women, said it was important for democracy that candidates accept election results.