The former head of Canada's largest pension fund manager assumed partial responsibility for the institution's enormous $39.8-billion loss in 2008, but defiantly defended his tenure and the performance at the investment giant.

Henri-Paul Rousseau, who left the Caisse last May, said Monday he was responsible for it having accumulated so much short-term assets called asset-backed commercial paper under his watch.

"I'll tell you straight off -- the ABCP situation developed when I was the top guy at the Caisse and, as such, I assume total responsibility," Rousseau said in a speech to the Montreal Board of Trade.

The Caisse held 30 per cent of Canada's ABCP and was stung in the fall of 2007 when the market suddenly froze when foreign banks took advantage of a loophole to renege on their requirements to maintain liquidity.

It took a $4-billion provision in 2008, on top of a $1.9-billion writedown in 2007.

Accumulating so much of the commercial paper was an error, but the Caisse needed somewhere to place the billions it earned in profits the previous years, he said.