Two Gold Coast theme parks in south-east Queensland have introduced new rules, banning people bringing their own food through the gates.
Brisbane mother Emma Gaunt says people are being caught out by Sea World and Movie World.
Ms Gaunt booked tickets to Sea World last Friday for her daughter's third birthday and says she was not told about the ban until they arrived.
"When we turned up to the gate we were greeted by some security guys who were pretty officious and they wanted to go through all our gear because the policy had changed as of the first of this month, the first of July, and we were no longer able to bring in food other than cut fruit or special dietary requirements," she said.
"I'd made a birthday cake, some quiches and we had a whole bunch of food to celebrate her birthday."
However, Warner Village Theme Parks says guests are welcome to use park grounds outside the front gates to eat their own food.
Guests with allergies, infants and babies, and pre-booked education groups are exempt from the policy.
Patrons will still be allowed to bring in fruit and bottled water.
Christopher Zinn, from consumer organisation Choice, says he is unimpressed with the ban.
Mr Zinn says the policy appears to be more about maximising revenue than coming into line with theme parks around the world.
"The admission costs are high, but they provide a good service, they're very popular - that's terrific and that should be enough," he said.
"But the point is you don't go to a theme park to eat - you go to a theme park to have fun, not have food.
"So the food is a convenience, it is an ancillary, but the fact that they would suddenly say that you can't take in your own food for us, or for me I should say, that is really crossing the line."
