I think that's objectively not true.  But successive politicians have claimed it to be so.  Plus the industry has a lot of people it hires to blow smoke.

Here's a Guardian study pointing out that Canada receives far less for resources, from the same companies, when they operate in other jurisdictions.

https://www.theguardian.com/environment/true-north/2017/oct/26/revealed-oil-giants-pay-billions-less-tax-in-canada-than-abroad?CMP=share_btn_tw