B.C.'s liability for cleaning up contamination left on Crown land by companies that may not have the money to deal with spills has jumped to more than half a billion dollars — with many of those sites containing mine waste, according to a new report.

The 2016 Crown Contaminated Sites Program report says the province is now liable for $508 million — an increase of $224 million over the past two years. But Andrew Gage, a lawyer with West Coast Environmental Law, says most of that is because of a change in how those sites are calculated.

"The province has actually started counting sites that were always there but which they hadn't previously counted," Gage said.

"There was a change in the accounting rules so even if they hadn't done an assessment of the site they can still recognize that they might have some liability connected to it."

All the same, Gage says the new dollar figure is a concern.

"It is alarming that there's that many sites out there," he said, referring to the 83 sites highlighted in the report — half of them considered a low priority.

The province said it will continue to prioritize contaminated sites across B.C. It said it will look at which ones need to be cleaned up immediately and which can be postponed.

Many of the contaminated sites detailed in the report are mine waste. In May, B.C.'s Auditor General released a damning report that found the government isn't prepared to protect the environment from disasters in the mining industry.

Gage said it's time the province strengthen its environmental laws.

"The mining companies need to know that if they cause this type of contamination, if they do measures that are going to make things worse, that they're not allowed to do, there will be consequences," he said.

Last week, the province announced the Mount Polley mine will reopen for the first time since the tailings pond disaster two years ago. It said the company has taken several measure to ensure the site is operating safety.

With files from Farrah Merali and Anita Bathe