With another country trashing Canada for allegedly sending it its waste, environmental groups are renewing their calls for the federal government to ban the practice outright.

Earlier this week, Cambodia followed Malaysia and the Philippines in publicly complaining about shipping containers filled with waste ending up at its ports.

At the same time, a collection of environmental groups — including Greenpeace and the Canadian Environmental Law Association — sent a letter to Environment Minister Catherine McKenna asking her to ratify an amendment to the UN pact known as the Basel Convention.

The amendment aims to bolster the original convention by barring the dumping of hazardous waste in developing countries.

"Shipping our wastes halfway around the world, allegedly for recycling, to countries that are already deluged with wastes is, as Canada well knows, a practice that is readily abused. It is a practice that is neither environmentally responsible nor just," reads the letter.

"We call on you to show the environmental leadership that Prime Minister Trudeau promised and support the ratification of the Basel Ban Amendment at the earliest possible date."

Ottawa is 'out of step:' activist

Kathleen Ruff, director of the human rights advocacy campaign Right On Canada, signed the letter. She said she's hoping it becomes an election issue.

"We believe that the minister and the government [are] out of step with the wishes of Canadians who are ahead of the government on this issue," she said in an interview, pointing to a recent Nanos poll showing nearly 80 per cent of Canadians believe Canada should manage and dispose of its own waste and recycling.

"[Just] because we have an affluent consumer lifestyle, that does not give us a free pass to trash the planet ... These countries are already swamped with an unmanageable problem of waste and plastics and we should not be contributing to that problem."

McKenna's office did not respond to CBC's request for comment.

Canada is a signatory to the original Basel Convention, which sets restrictions on shipping waste, but has come under fire for continuing to send plastic waste to developing countries.

In a recent high-profile case, Canada shipped 69 containers of rotting garbage from the Philippines back to Vancouver to end an escalating diplomatic spat with Manila at a cost of more than $1 million.

Environmentalists march outside the Canadian Embassy to demand the Canadian government speed up the removal of containers of garbage that were shipped to the country Tuesday, May 21, 2019, in Manila, Philippines. (The Associated Press)

The containers originally were shipped to the Philippines by the now defunct export company Chronic Inc. in 2013.

Government looking into Cambodia case

Malaysia also has expressed a desire to return shipments of Canadian trash, with Malaysian Prime Minister Mahathir Mohamad calling it "grossly unfair for rich countries to send their waste to poor countries simply because poor countries have no choice."

Cambodia says 83 containers weighing 1,400 tonnes — 13 of them allegedly Canadian — were discovered in Sihanoukville, the country's main port.

"Cambodia is not a dustbin where foreign countries can dispose of out-of-date e-waste, and the government also opposes any import of plastic waste and lubricants to be recycled in this country," said government spokesperson Neth Pheaktra.

Environment and Climate Change Canada said it is looking into the Cambodia case.

"We are aware of the concerns raised by the Cambodian government and have reached out to their officials through our embassy in Phnom Penh for further details. We are following this matter closely," said spokesperson Bronwen Jervis in an email to CBC News earlier this week.

In 2016, the Canadian government amended its hazardous waste and recyclable laws and has argued that means the shipment sent to the Philippines in 2013 and 2014 would be prohibited today.

Ottawa also says it hasn't issued permits for Canadian companies to ship hazardous household waste overseas since the regulations changed three years ago — raising questions about how Canadian waste keeps showing up in other countries.

The issue of cross-border disposal has become a growing problem after China, previously a primary destination for trash shipments, banned imports of almost all foreign plastic waste early last year.