The Equality Campaign says the text messages it blasted out across Australia over the weekend drove 170,000 people to click through and seek information on the same-sex marriage postal survey.

According to the "yes" camp, another 20,000 signed up to volunteer as a result of the weekend campaign, which some recipients and critics - including Australian Christian Lobby managing director Lyle Shelton - have argued was an invasion of privacy.

Responding to concerns, the Australian Communications and Media Authority said on Monday that the sending of unsolicited calls, emails or SMS messages like this does not break any laws if it is not promoting or selling a product or service.

"Communications about political matters do not usually include a commercial element," the ACMA said, absolving the Equality Campaign of any breach under the Do Not Call Register Act or the Spam Act.