Sky News has earned a slap on the wrist from the media regulator after a pro-marriage equality advertisement was aired on The Bolt Report without an appropriate disclosure.

The 30-second ad featured a surgeon, surf lifesaver, firefighter and military officer urging politicians to legalise same-sex marriage.

It aired during an ad break for Andrew Bolt's conservative talkshow, and also featured a banner that looped across the bottom of the screen alongside the day's headlines.

The Australian Communications and Media Authority received a complaint arguing the ad should have come with the usual political disclosure. The disclosure announces which person or political party has authorised the advertisement immediately afterward.