One in 10 childcare centres in Australia has never been rated by regulators and others don't meet the standards, leaving tens of thousands of children in facilities that fail national benchmarks. 

A Four Corners investigation has exposed a flawed, inconsistent regulatory system and a shortage of childcare workers that has resulted in some centres cutting corners, hiring unqualified staff and eroding the overall quality of care.

With centres reassessed on average every four years, and some gaming the system, parents can't be sure their child's centre meets the standards or that staff are properly trained or qualified.

All centres are required to have a quality rating, ranging from "exceeding" standards to "meeting" standards, "working towards" and "significant improvement required".

Gabrielle Meagher, who has studied privatised social service systems for decades, said government policy and the patchwork of state-based regulators had not kept pace with the growing sector, which now generates more than $20 billion a year and is dominated by for-profit operators.

"Ten per cent of all centres don't have any quality rating. Most of those are for-profit," Professor Meagher said.

"These [are] emerging chains that are growing rapidly, some of which are allowed to keep opening centres even though they might have some of their centres working towards the quality standards."

"Working towards" is the rating given when a centre doesn't meet quality rating standards. These centres are allowed to keep operating.

NSW Greens MP Abigail Boyd said the ratings system was "a joke".

"This really stupid term of working towards … That is a failure to meet the minimum standards expected under the national law. And yet those centres are just allowed to continue [to operate] year after year without ever meeting standards," Ms Boyd said.

"It's about creating this viable industry and then we just chuck these ratings on the top and pretend that there's some sort of actual accountability or scrutiny going on."

Four Corners has found that up to 47,000 kids are registered in for-profit long daycare centres that don't meet national quality standards, compared to 8,500 kids in non-profit centres.

'Appalling to see'

To get a rating of "exceeding" a centre must pass seven quality areas. These include the centre's educational program, overall health, safety and wellbeing, the physical environment and qualified staffing arrangements.

Only 14 per cent of for-profit centres exceed the national quality standards, while non-profits are more than double that rate.

Watch Four Corners's special investigation into the systemic issues plaguing Australia's childcare sector on ABC TV and ABC iview.