Following horrific claims of abuse at some early learning centres, the federal government has issued notices to more than 60 providers which have either broken the law or put children at risk.
Thirty of the operators have until the end of February to fix the issues, while another nine are facing consequences for failing to act before an earlier deadline.
The majority of the nine are daycare providers, AAP understands.
They risk having their eligibility for government childcare subsidies revoked - a move which would make the businesses unviable.
Education Minister Jason Clare said he hoped to send a strong message to providers that meeting minimum standards was not optional.
"I think any reasonable Aussie hearing that for the first time would think well, if you're not prepared to meet the standards, then you shouldn't be receiving taxpayers' money," he told reporters in Sydney on Friday.
"This is not an idle threat. I'm not mucking around here."
Friday also marks the start of mandatory child-safety training for staff in the early learning sector, and a national register of workers.
More than 100,000 employees across Australia had already registered for the training, the government said.
The $45 million national register aims to better track childcare staff as they travel across states and territories.
It will also keep records of employees' qualifications, working-with-children checks and other identifying information.
The reforms follow a series of allegations about children being abused in early learning centres.
In one of the most egregious alleged cases, Melbourne man Joshua Dale Brown has been hit with more than 150 charges, accused of abusing 12 children.
His case remains before the courts.
Advocacy group The Parenthood backs the government's reforms, urging it to go further and set up a new national body to oversee the childcare sector.
"Reform can't stop here," chief executive Georgie Dent said.
"The steps taken so far have made early learning safer, but without consistent national oversight, enforcement will remain uneven and quality standards will continue to depend on where a family happens to live."
Lifeline 13 11 14
Kids Helpline 1800 55 1800 (for people aged 5 to 25)
National Sexual Abuse and Redress Support Service 1800 211 028
