Australian Beverages Council chief executive Tony Gentile told a Senate committee hearing that there was no link between obesity and advertising.
"Why regulate something where there is no proof there is a cause and effect?" News.com.au quoted him, as saying.
Legislation, being proposed by the Australian Greens, failed to address factors contributing to obesity, including inactive lifestyle.
According to Gentile, obesity rates had not fallen when advertising restrictions on junk food had been introduced elsewhere.
Food manufacturers used the hearing to defend their plan to introduce an industry code of conduct for advertising.
The code bans advertising unhealthy foods, directed at kids under 12, during children's programs.
"We fully accept the comments that some people have made about self-regulation and we believe it is up to us to prove them wrong," Australian Food and Grocery Council chief executive Kate Carnell said.
She said that the legislation's heavy-handed ban did nothing to encourage promotion of healthy food and lifestyles.