Los Angeles: US presidential hopeful Ted Cruz's claim sexual assaults on women in Australia went up significantly after strict gun laws were introduced has been challenged by a Washington Post analysis.

Senator Cruz said on high-profile American radio host Hugh Hewitt's show on January 12 Australia's post-Port Arthur massacre gun legislation meant women were unable to defend themselves from being raped.

The Washington Post's Fact Checker column examined Senator Cruz's comment and on Monday rated it a "whopper" of a factual error, the highest rating on its "Pinocchio Test".