Labor 'shutting down' marriage debate

Senior Liberal senator Zed Seselja says Labor is attempting to stifle free speech by criticising an advertisement advocating a "no" vote on same-sex marriage.

Labor leader Bill Shorten says the television ad - in which one woman says her son had been told he could wear a dress to school next year if he wanted - is "offensive and hurtful" to same-sex families.

"These mothers are clearly putting the case that their ability to object to fairly radical sex education in schools and the like will be much harder if you redefine marriage in the Marriage Act," Senator Seselja told the ABC on Wednesday.