Environment Minister Greg Hunt has threatened to introduce a law to ban microbeads, the tiny particles that are found in face scrubs and body washes, if companies do not adhere to a voluntary phase-out.

As state and federal ministers met for the roundtable on plastic bags in Sydney today, Mr Hunt said the government was taking a "stronger stance" on this "important environmental issue".

"We will continue to work with companies towards a voluntary phase-out of microbeads," Mr Hunt said in a statement.

"However, if by 1 July 2017 it is clear that the voluntary phase-out will not achieve what is effectively a widespread ban on microbeads, the Federal Government will take action to implement a ban in law."

Under the Government's current plan, companies in Australia have the option to remove microbeads from their products by July 2018.

But environmentalists have criticised the voluntary ban, saying the Government needs to be tougher, and pointing to recent legislation passed in the United States that has banned the production and sale of products containing microbeads by July next year.

The beads are smaller than 5 micrometres in size and are used as exfoliations in face scrubs, toothpastes and cosmetics, replacing natural ingredients such as walnut kernels.

Last month, 7.30 revealed that fish in Sydney harbour were swallowing the tiny plastic particles.

Scientists estimate there are about 300,000 microbeads in an average bottle of face scrub, usually labelled as polyethylene in the product ingredients, or HDPE (high-density polyethylene), or even PEHD.

At the time, an industry spokesman from the group Accord, Craig Brock, told 7.30: "In hindsight, it was probably something that people weren't aware could happen."

"It all relates to what happens to the waste coming from our households," he said.

Jon Dee, who has been running a campaign against microbeads, was pleased with the announcement.

"Given that we also have billions of plastic microbeads ending up in our waterways, we welcome Minister Hunt's announcement," he said.

The companies that have agreed to the voluntary phase-out include Unilever, L'Oreal, Beiersdorf (which manufactures Nivea products), Reckitt Benckiser (which manufactures Clearasil products), Johnson and Johnson, The Body Shop, Ella Bache and Clarins.

Supermarket giants Woolworths and Coles have also committed to phase out their own products containing microbeads.