The consumer watchdog has not ruled out enforcement action over smartphone and tablet apps that claim to be free but charge once the user is engaged in the game.

More than 50 consumer protection agencies around the world are today launching a push against smartphone and tablet apps that mislead children into making unauthorised purchases.

The Australian Competition and Consumer Commission (ACCC) says many apps claim to be free but when children download them and begin playing the games they inadvertently end up paying money to keep participating.

Deputy chair Delia Rickard says the ACCC and other consumer groups around the world have received complaints parents about the issue.

"One of the messages we keep hearing from parents is kids get frustrated, to get to the next level you actually have to make a purchase or something that happens instantly with a purchase can take days of playing to get there, so they've really tried to tamper with psychology and understand kids psychology to play into that, to try and maximise the chance ... of purchases being made," Ms Rickard said.

"I think you could have much better disclosure.

"With some of these, certainly when you download from Google it's not at all clear, you find these games in the free section of the stores and with some it's not clear at all that there are in-app purchases, yet with some of these games where there is no forewarning, you pay over $100 for a container of virtual doughnuts. Now, who in real life is going to pay over $100 for some doughnuts?

"Apple's got slightly better disclosure. It will tell you there are in-app purchases, but you really need to scroll down and look to see what's the maximum purchase price, what's the minimum, what's the maximum and to understand whether or not to progress in the game you need to make purchases."

Ms Rickard says the ACCC will be speaking to Google and Apple to express its desire for better disclosure of the cost of in-app purchases.

"We will see, we certainly have contacted Apple and Google to express our concerns. We'll be meeting them soon. I know that Apple's already made some improvements," she said.

"It's an exercise aimed at informing us, informing parents and kids and then engaging them to get changes and we'll determine down the track whether or not any enforcement action eventuates from this as well.

"It will be an option if disclosure isn't improved but we need to look at this on a case-by-case basis."

A number of parents have told the ABC that their children have been able to spend hundreds or thousands of dollars on in-app purchases.

Simone de Kretser regularly allows her three children to download free apps - but she has now found out they are not always free.

"They'd ask me if they could install a particular app and it was free, and I said, 'sure, you can have that no problem', signed in, let them download the app and off they were playing quite happily.

"They had a friend over and it was all fine, they were in their room playing for a long, long time, and low and behold before I knew it they'd racked up $550."

Mrs de Kretser says the games play on the competitive nature of children.

Her family has managed to tally a bill of almost $2,000 using a number of apps.

"To lure the children into going to the next stage or the next level and those sorts of things they need to get either coins or tickets of this or whatever and to do that they might have to wait 24 hours before they earn that, but if they want to get to that level straight away they have to do a purchase."

Rob Gorton has two daughters and says he is reasonably tech-savvy.

He says when his four-year-old daughter asked to download a game, he checked to make sure it was free before giving her the green light.

He soon found out it wasn't free, even though he had the right account settings switched on so that no purchases could be made.

"My other daughter was watching her play it at the time and said that she'd been playing the game, it was a game where you planted different types of crops, and they grew and it prompted you to help things speed up if you made purchases in the store.

"Because I'd had entered my password it remained active for 15 minutes and she was able to make in-app purchases even though my account settings had in app purchases turned off."

Mr Gorton feels lucky the bill only reached $50 before he found out what was going on.

"I do feel very lucky with that because a friend of mine went through a similar thing and her son at a similar age racked up about a $600 bill making in-app purchases."

Another parent has told the ABC her 13-year-old daughter spent $700 playing a game on a tablet that her parents bought her as a year seven school requirement.

Another child spent $260 on two games.

Paul Bendat, an independent advocate for gambling reform, says the situation has raised two main concerns.

"One, that the proliferation of these apps leads to normalisation of gambling. Secondly, by the use of in-app purchases, they essentially prey on kids under 18 who have some sort of access to an iTunes store or an Android store.

"You make these purchases simply so you can continue playing what is most frequently a poker machine simulation."

Mr Bendat says there is a role for government to beef up legislation in the area.

"It's better safeguards in place, I think it's clear that Commonwealth does have the jurisdiction to regulate matters like this. It may well be that the states do as well under their consumer protection laws, but clearly it's the responsibility of the Commonwealth."

Mr Bendat has likened reform in this area to that of gambling advertising in sport.

"Tony Abbott made it very clear that if the industry does not self regulate that the Commonwealth had the power to legislate with respect to the advertising of live odds within sporting events.

"He has that same power to legislate to either remove or better regulate these sort of applications from things like iTunes stores or Facebook."

The ABC contacted Apple and was directed to the company's website.

The website says "you can enable Restrictions, also known as Parental Controls, on an iPhone, iPad or iPod touch to prevent access to specific features".

And, "The range of features includes the ability to prevent access to specific content types such as In-App Purchases".

Earlier this year, Apple agreed to settle a US class-action lawsuit for $100 million agreeing to refund parents in cash or credits for its iTunes store.

The suit was launched after the parents of a nine-year-old girl from Pennsylvania complained the girl bought $200 of virtual money from three "free" games.

Google says the latest Android operating system can restrict in-app purchases.