Advanced countries such as the U.S., Canada and Japan should stop the “grossly unfair” practice of sending non-recyclable waste to poorer countries, Malaysian Prime Minister Mahathir Mohamad said Thursday.

Mahathir’s comments during his visit to Tokyo came days after his government announced plans to return thousands of tonnes of imported plastic waste back to where it was originally shipped.

“It is grossly unfair for rich countries to send their waste to poor countries simply because poor countries have no choice, and maybe it contributes a little to their economy,” Mahathir said at a news conference. “We don’t need your waste because our own waste is enough to give us problems.”

China banned the import of plastic waste last year, leading several Southeast Asian nations to become new targets.

In the Philippines, a cargo ship arrived in a northern port on Thursday to pick up and return 69 containers of garbage to Canada. Officials say the trash was shipped illegally to the Philippines in 2013-2014.

“You give us the waste then you are going to have us insist that we pollute the environment by getting rid of the waste,” Mahathir said. “But please remember that when you pollute one part of the world, you pollute the rest of the world also.”