Niall Ferguson is not a man who shies away from controversy. Nor, as a Scottish professor of history who jumped ship from Oxford to Harvard eight years ago and who said earlier this year that he was permanently leaving the UK for America's superior "quality of intellectual life in my field", is he a man who is frightened of expressing forthright opinions.
This time, however, those opinions have ruffled some heavyweight feathers on Professor Ferguson's preferred side of the Atlantic.
Professor Ferguson, once an adviser to the 2008 Republican presidential nominee John McCain and who delivered the prestigious BBC Reith Lectures earlier this year, has stirred up a hornets nest with his cover story for Newsweek under the headline: "Hit the road, Barack."
The article asks if President Obama has delivered on his promises, "and the sad truth is he has not". It goes on to allege that the president has broken campaign promises, and criticises his stimulus package, his foreign policy record and his healthcare reform.
The piece provoked a sharp response from commentators in the US, among them Nobel Prize-winning economist Paul Krugman, who has crossed swords with Professor Ferguson in the past and yesterday accused the Briton of "unethical commentary" and "deliberately misleading readers".
Professor Krugman's response, for the New York Times, slammed the Newsweek piece for its "multiple errors and misrepresentations" adding: "We're not talking about ideology or even economic analysis here – just a plain misrepresentation of the facts."
He was particularly exercised about Professor Ferguson's comments on Mr Obama's healthcare reform, saying it would not increase the deficit as Professor Ferguson wrote, but in fact do the opposite.
Last night the spat showed no sign of abating, with Professor Ferguson responding: "You know you have hit the target when Paul Krugman takes time out from his hiking holiday".
But Professor Krugman has not been alone in his critique of the Glasgow-born academic, who once described himself as a "fully paid-up member of the neo-imperialist gang" and is known for his defence of the British empire.
By last night a series of publications were rushing to pick holes in the Newsweek article. Several correspondents at The Atlantic took Professor Ferguson to task, including associate editor Matthew O'Brien who carried out an extensive "fact-check" on the piece. Matthew Yglesias, Slate's business and economics correspondent, said Professor Ferguson's attack on Mr Obama's time in office was "so comprehensive as to be completely incoherent".
Fighting talk: Ferguson's 'facts'
"The President pledged that health-care reform would not add a cent to the deficit. But the CBO and the Joint Committee on Taxation now estimate that the insurance-coverage provisions of the ACA will have a net cost of close to $1.2tn over the 2012-22 period."
"He promised to 'build the roads and bridges, the electric grids, and digital lines that feed our commerce and bind us together'. He promised to 'restore science to its rightful place and wield technology's wonders to raise health care's quality and lower its cost'. And he promised to 'transform our schools and colleges and universities to meet the demands of a new age'. Unfortunately the president's scorecard on every single one of those bold pledges is pitiful."
"The question confronting the country nearly four years later is not who was the better candidate four years ago. It is whether the winner has delivered on his promises. And the sad truth is that he has not".