A new report says 11 million litres of toxic water leak each day from giant waste ponds used by the oilsands industry in northern Alberta.

11 Million Litres: the Tar Sands' Leaking Legacy was released Tuesday by Environmental Defence, a Canadian advocacy, research and education group.

The study used the leakage rates each company cited in their project applications and added them up, applying an average leakage rate for projects that did not publicly disclose this information.

"We had read a lot of the company proposals for new tarsands projects and realized companies themselves were saying that all of these ponds leak," report author Matt Price said.

The amount of liquid that leaks each year would fill Toronto's Rogers Centre two and a half times, Price said.

Price said the figure of 11 million came from the most conservative of the models the group used in the report. He believes the amount is much higher.

Preston McEachern from Alberta Environment disagrees with the amount of seepage cited in the report. He said any seepage that does get out goes into aquifers which are already contaminated because they flow through the oilsands.

Alan Fair, the manager of research and development for Syncrude, wouldn't comment directly on the figures in the Environmental Defence report, but said his company closely monitors groundwater quality in the area around its tailings ponds.

"We on a regular basis report and review those results with Alberta Environment, and I can tell you that they, nor ourselves at this point ... have any immediate concerns with the quality of that water," he said.

But Matt Price said part of the problem is that the industry is monitoring itself and the results it sends to Alberta Environment are not publicly available.

"Each company is ... only monitoring its own backyard but who's looking at the bigger picture here?" he said.

"Even though this is just four billion litres a year now that's leaking, our projections are it's going to go to 25 billion litres a year within a decade. Can the ecosystem actually absorb that amount of contaminated water? Who's doing those studies? Who's asking these questions?"

With files from the Canadian Press