Salvation Army stores sustainability manager Donald Munro said while dumped rubbish was a problem at all stores, Lalor was one of the worst.

About 75 to 80 per cent of everything left outside the store was rubbish, he said.

"What we're seeing in terms of what's dumped couldn't even loosely be construed as donatable goods," he said.

Items dumped at the Lalor store include the shells of televisions, kitchen waste, old mattresses, broken furniture and electrical appliances and chicken scraps.

"It's pretty horrific for volunteers to face that every day," Mr Munro said.

He said dumpers drove to the back of the Lalor store and offloaded rubbish from trucks and trailers at night.

"Unfortunately genuine donations are also being rummaged through, so anything trendy or with a good brand is taken and bags of clothes are ripped open and scattered on the pavement," Mr Munro said.

Lalor Traders Association spokeswoman Noella Jacobs said rubbish dumping outside the store had been an issue for years.

"We're just trying to educate the community to try to stop people taking advantage of the Salvation Army," she said.

The Environment Protection Authority conducted a trial blitz outside op shops in November and is reviewing the results to determine future support for local councils.

The EPA has the power to fine litterers up to $244 for dumping rubbish.