Desperate parents unable to find a childcare centre or afford a nanny are using Gumtree or social media to hire foreign au pairs with limited experience and qualifications as a "cheap form of child care".
Nanny agencies warned of the "risky" practice in their push for private in-home child care to be eligible for the Federal childcare rebate.
In a submission to the Productivity Commission's childcare inquiry, Dial-An-Angel national chief executive Danielle Robertson said families were exploiting au pairs by using them as underpaid full-time nannies.
"This is extremely risky for desperate parents who haven't any other options," she said.
Some au pairs lacked experience, qualifications, first aid training, working with children checks and criminal checks. They could live and work with a family for six months on a working holiday visa and though supposed to be "an extra pair of hands", some had full-time childcare duties.
Dial-an-Angel WA manager Kate Spencer said some people who wanted to hire a nanny found they could not afford one.
Often they ended up hiring someone off Gumtree, who usually did not have the checks, certificate or experience her staff had. While not ideal, she could understand why some families resorted to it.
Dial-an-Angel has joined the Australian Nanny Association in calling for the childcare rebate to be extended to approved in-home private care.
Heather Smaellie, from Perth Au Pair & Demi Pair, urged parents to use an agency approved by the Cultural Au Pair Agency of Australia.
They only placed au pairs who had police and medical clearances and ensured they got a working with children clearance once in Australia.
The au pair industry was also pushing for the childcare rebate to be expanded and to have an au pair visa, which Rebecca Neveldsen, from the Australian Nanny and Au Pair Network, said would allow flexibility.
"Many of our families need childcare help outside the hours of a day-care centre," Mrs Neveldsen said.
Perth mother-of-two Paisha Cook hired a German au pair through Mrs Neveldsen's agency and said she had become part of the family.
"The only thing I don't like is we can only have them for six months," she said. "It would be great to have more flexibility.
"It's important to go through an agency. We want our au pairs to know we're a safe family and that we've been background-checked - and they are also background checked."