Distressed asset king Marc Lasry says energy debt is a 'once in a lifetime opportunity' right now

After a collapse in oil prices, some energy companies that looked promising just a couple of years ago are now stumbling.

But at least one hedge fund manager thinks that the debt issued by those struggling energy firms is a goldmine.

Marc Lasry, CEO of Avenue Capital Group called energy debt "a once-in-a-lifetime opportunity" at a Reuters conference on the global investment outlook.

Avenue Capital Group focuses specifically on distressed debt, buying up securities issued by companies which are actually in or near bankruptcy.

He added that he believes that the strategy will work whether the energy company whose debt he's purchasing goes under or not: "Either you get paid off, or you will become the new equity of these companies," adding that it wasn't a short-term strategy, and would only pay off after a few years.

According to Reuters, Lasry added that "the whole market is oversold," giving the example of senior secured debt selling for $0.40 on the dollar. That sort of corporate debt is less risky to investors, because it's given repayment priority if the company is liquidated.

And if the debt was to climb back towards trading at its face value, an investor would have effectively been given a 60% discount.

Buying into companies that have already gone bust, or which are at serious risk of doing so, isn't a financial strategy for the weak-hearted.

Lasry's thesis is based on his view that oil prices will come back from their current levels, which have been extremely low in comparison to recent years. A barrel of Brent crude oil currently trades at about $44, down from over $80 this time a year ago, and over $110 two years ago. He was banging the same drum back in January, noting that energy debt was over-sold on the assumption that oil prices would rise to $70 per barrel or above by early 2017.