It was perhaps the costliest ad lib in political history, 90 seconds of ill-judged, ill-timed bile that helped to kill off any hope of consensus on Capitol Hill.

That was the charge against Nancy Pelosi after Congress’s rejection of the $700 billion Wall Street bailout plan yesterday, a rejection that Republicans blamed directly on her aggressive and overtly partisan speech shortly before the vote.

As Speaker of the House and second in line to the presidency after Dick Cheney, the most powerful woman in US political history has never been one to keep her thoughts to herself. Even at a time of national crisis she can be relied on to have a dig at President Bush.

But as she deviated from her prepared remarks on the floor of the House yesterday, Ms Pelosi appears to have gone too far. At a time of heightened sensitivities all around, she deployed the C-word — Clinton — and helped to give a group of Republicans the excuse they were waiting for to walk away from the bailout.

Ms Pelosi started off by stating the obvious: that $700 billion was a “staggering figure”, a figure that had prompted a “very informed debate on all sides” of which she, as Speaker, was duly proud.

But that was as far as her evenhandedness went. She was not going to let this moment go without making clear who she felt was to blame for this whole mess.

Picking up on the size of the bailout package again, Ms Pelosi said: “Seven hundred billion dollars: a staggering number, but only a part of the cost of the failed Bush economic policies to our country, policies that were built on budget recklessness.

“When President Bush took office he inherited President Clinton's surpluses — four years in a row, budget surpluses on a trajectory of $5.6 trillion in surplus. And with his reckless economic policies within two years he had turned that around and now eight years later the foundation of that fiscal irresponsibility, combined with an anything-goes economic policy, has taken us to where we are today.

“They claim to be be free-market advocates when it’s really an anything-goes mentality: no regulation, no supervision, no discipline. And if you fail you will have a golden parachute and the taxpayer will bail you out. Those days are over. The party is over in that respect.”

She added: “Democrats believe in a free market. We know that it can create jobs, it can create wealth, it can create many good things in our economy. But in this case, in its unbridled form as encouraged, supported by the Republicans — some in the Republican Party, not all — it has created not jobs, not capital, it has created chaos.”

John Boehner, the Republican House Minority Leader, said that Ms Pelosi’s speech had “poisoned” the Republican caucus and “caused a number of members we thought we could get to go south” — making the difference in a 228-205 vote.

He added: “I do believe that we could have gotten there today, had it not been for the partisan speech that the Speaker gave on the floor of the House. We put everything we had into getting the vote to get there today.”

Roy Blunt, a House Republican whip, said that party leaders had thought that they had a dozen more votes going to the floor than they actually had but there was “so much partisan discussion in what should have been a bipartisan effort to solve this problem for the American people”.

Ms Pelosi herself, predictably enough, rejected any suggestion that she was to blame for the defeat of the bailout. “You don’t vote on the speech, you vote on the Bill,” an aide said.

In The New York Times, the commentator David Brooks struck a more balanced tone, accusing House Republicans of confusing "talk radio with reality" in their drive to defeat the Bill and pointing out that 95 Democrats had voted against the bailout.

He added: “Pelosi’s fiery speech at the crucial moment didn’t actually kill this Bill, but did she have to act like a Democratic fund-raiser at the most important moment of her career?"

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