The advertising standards board announced it had dismissed complaints about a controversial anti-horseracing billboard just hours after the death of two Melbourne Cup horses.

The billboard, depicting a dead horse lying on its side, was pulled from Melbourne's CityLink freeway after objections from the landowner last month.

The image was accompanied by the text "Is the party really worth it? Horseracingkills.com".

A complainant to the Ad Standards Bureau called the billboard "disgraceful and not true" and said it was disturbing for children.

"I own horses and they are treated with great respect and care," the complainant said.

"People should not be subjected to gross images of dead animals whilst driving. It's also upsetting for children."

The board's decision was made on October 22 but was not made public until Tuesday afternoon, shortly after the deaths of Melbourne Cup favourite Admire Rakti and seventh-place-getter Araldo.

It said whether the advertisement was misleading was not a matter for the bureau's complaints board to determine.

It also said, while the name of the website could suggest the horse was dead, "the lack of blood or obvious trauma to the horse means that people, particularly children, could consider it to be asleep".

The billboard was posted by the Coalition for the Protection of Race Horses, an organisation calling for reforms to the thoroughbred racing industry, including the banning of whips.

Their campaign director Elio Celotto said the group had struggled to find alternative advertisers in the wake of the controversy and was now advertising on mobile billboards.