Canada's GDP per capita may be slowing, but it's hard to blame the "leftist policies" specifically. As we like to say around here, correlation is not causation. So let's have a look at some other countries to see how they've fared. We'll take the US and some other more leftist countries and look at change real GDP per capita.
Country 2000-2006
US..............1.5%
Canada..........1.5%
Norway..........1.7%
Spain...........1.7%
Sweden..........2.3% (!)
UK..............2.1%
France..........1.0%
Germany.........0.9%
Netherlands.....0.9%
Denmark.........1.3%
Australia.......1.8%
http://www.bls.gov/fls/flsgdp.pdf
As you see, growth is pretty all over the map. Some leftist countries out perform the US; others do not. So to say that "leftist policies" are hurting Canada's growth is, on its face, incorrect. Perhaps it is just the fault of the specific leftist policies, but certainly not of leftist policies at large.