What was once no more than a day off for a BBQ and a game of backyard cricket has all of a sudden morphed into a commercial enterprise overflowing with Australia Day merchandise from baby clothes to bikinis– and it’s here to stay, according to the experts.

Bill Proud, marketing lecturer at QUT in Brisbane, said Australia Day had been one of the last public holidays not overtaken by commercialism – that is, until a couple of years ago when retailers decided to up the ante.

"Australia Day really was that last bastion, the untouched public holiday where people spent it with their families relaxing with a couple of beers and maybe watching the cricket," Mr Proud said.

"All of a sudden, the past couple of years have seen this explosion of Australia Day merchandise and it’s just become ridiculous."

At fashion store Supre in Brisbane’s CBD, Australia Day singlets and t-shirts were selling like hotcakes, while Big W was nearly sold out of its "All Australian Baby" range.

Bakeries, restaurants, bottle shops and grocery stores all flogged their "Australia Day" products while newsagents across Brisbane were nearly sold out of temporary tattoos and flags.

Consumers were not the driving force behind the new tradition of Australia Day singlets and baby bibs, Mr Proud said.

"It’s all being driven by the retailers. They’ve identified a market and are now changing the face of Australia Day with all these products," he said.

"They’ve turned a cultural celebration into a commercial enterprise and it won’t be going away anytime soon."

Murray Berghan, managing partner of Brisbane firm Make Communications, agreed the commercialism was here to stay but said it was not necessarily a bad thing.

"As a proud Australian, and a marketing professional, if there is ever a public holiday that I would want to become commercialised it is Australia Day – as long as the goods are made in Australia," he said.