PARENTS say they are disgusted and angered by claims a children's play centre in Melbourne's southeast was used to host a sex party for swingers after hours.

A furious reaction exploded online yesterday when parents allegedly discovered an advertisement with explicit photographs inviting swinging couples to a party at the venue with "many features like a laser light show, fog machine, giant ball pit and jumping castle''.

Shocked mothers gathered at Casey Kids Play House Cranbourne demanding answers and their money.

City of Casey manager of planning Duncan Turner said the play centre had been issued with a planning contravention notice.

“Council is currently investigating reports that the Casey Kids Play House is allegedly being used for a purpose outside its planning permit,” he said.

“While Council continues its investigations, a Planning Contravention Notice has been issued to the operators.

“This requires the immediate cessation of the use of the land for purposes outside its planning permit.”

Carrum Downs mother Stacey Derks said she had a dual birthday party for two of her children, 2 and 4, at the venue in May.

"It was a really, really good day, everyone had such a good time, but now we're very disturbed, my kids were there and all my friends kids were too, we're worried about what they could have been exposed to,'' Ms Derks said.

She said her children had shown no signs of sickness, but she would be asking her GP if there were any risks.

Irate mother of one Sarah Perry said she was disgusted by the ad.

She had her son's first birthday at the venue in May.

"My son is one he puts balls in his mouth and everything, god knows what STDs could be in there,'' she said.

In a post purporting to be from the play centre's Facebook page - but later deleted - it said there was no intention to "host any type of party of this description''.

It said they had taken over the business in March.

"We are trying to get to the bottom of this very disturbing issue and potential damage to our reputation and will keep you up to date,'' it read.

"The (centre) is booked out on weekends for catered kids birthday parties and also for private hire when we are not there.

"We give them the keys and show them how to open and close everything.''

"Thank you for your understanding and support.''

The centre's owners could not be contacted yesterday.

- with Peter Strachan