A ban on plastic bags is being phased in across the ACT from today.

There will be a four month transition period for businesses, before plastic bags are completely banned in November.

Environment Minister Simon Corbell says shops can supply bags during the transition period.

"As long as they also provide an alternative which is permitted under the legislation such as a reusable bag or a biodegradable bag or a paper bag," he said.

"This is the transition period to get consumers used to the fact that the ban is coming."

Mr Corbell says retailers must educate consumers about the changes.

"Bags that will not be banned are heavier bags used for example at clothing outlets and the barrier bags that are used to store fruit and meat, they will continue to be made available," he said.