• Expert joins attack on TV guru savaged by Jon Stewart • Tipster has proclaimed the downturn is already 'over'

Wall Street's favourite jester has fallen foul of the prophet of doom. A tense feud has broken out between the outspoken tele­vision stockpicker Jim Cramer and the notoriously gloomy economist Nouriel Roubini.

Roubini, a New York University professor who famously forecast a dire world recession as far back as 2006, has taken exception to remarks on a blog by Cramer that he is "intoxicated" with his own "prescience and vision" and is refusing to see green shoots of recovery in the financial markets.

"Cramer is a buffoon," said Roubini. "He was one of those who called six times in a row for this bear market rally to be a bull market rally and he got it wrong."

The confrontation pits two of the financial world's biggest egos against each other. While Roubini has won plaudits for correctly predicting that the credit crunch would cause a domino effect around the world, Cramer has long been a cheerleader for mass participation in the stockmarket.

Cramer's CNBC show, Mad Money, has come under repeated attack in recent months for its bullish enthusiasm in a highly volatile environment. The comedian Jon Stewart recently roasted Cramer and the broader financial media for missing warning signs of a "once in a lifetime financial tsunami".

Roubini, who believes the situation is so gloomy that leading US banks may need to be nationalised, was dismissive of Cramer: "After all this mess and Jon Stewart, he should just shut up because he has no shame."

Speaking to the Associated Press ahead of a speaking engagement in Toronto, the economist continued: "He's not a credible analyst. Every time it was a bear market rally he said it was the beginning of a bull, and he got it wrong."

With his catchphrase "boo-ya" and a variety of colourful props, Cramer, 54, is a household name in the US. A former hedge fund manager, he casts himself as a self-made man who was once so impoverished that he had to sleep in his car. He took prolonged flak last year for telling viewers that Bear Stearns was "not in trouble" just a week before the 85-year-old investment bank collapsed – a remark which, he insists, was misinterpreted and taken out of context.

But Cramer has continued to attack doom-mongers, recently referring to Roubini and the Nobel prize-winning economist Paul Krugman as part of a "nationalisation jihad" for their advocacy of public intervention in the financial sector.

Last week, Cramer told his viewers that the recent 20% rally in Wall Street markets was sufficient to judge that the downturn was past its worst: "Right now, right here, on this show – I am announcing the depression [is] over!"