After decades of struggle and months of political in-fighting, Barack Obama stood poised to sign into law historic reforms to America's healthcare system. But first his vice-president had to have his foot removed from his mouth.

At a White House ceremony for Obama to seal passage of the legislation by giving it his signature, vice-president Joe Biden gave an introduction praising Obama's leadership. "Mr President, you're the guy that made it happen," he said, before embracing Obama and excitedly whispering in his ear: "This is a big fucking deal!" The aside may have been meant for Obama's ears alone but it was picked up the microphone on the podium and broadcast to the watching television audience of millions.

Applause drowned out Biden's comment to the dignitaries in the East Room but the reaction on blogs and cable news channels was instantaneous. "The vice-president used a word that most of us would never use in front of our mother," said CNN anchor Rick Sanchez, explaining why his network bleeped out the remark in its replays. Ben Smith, a blogger for the Politico website, labelled it: "The mother of all Biden moments."

Shortly after, White House press secretary Robert Gibbs embraced Biden's slip, by writing on Twitter: "And yes, Mr Vice President, you're right."

It certainly isn't the first time that Biden has let his tongue get the better of his brain. Long before Obama chose him to be his vice-president, Biden was renowned for his gaffes. During the Democratic presidential primaries, Biden apologised for describing Obama as "the first mainstream African-American who is articulate, and bright and clean, and a nice-looking guy". In 2008 Biden urged a wheelchair-using local politician at a rally in Missouri: "Stand up', Chuck, let them see you."

Biden isn't the first vice-president to resort to Anglo-Saxon. Dick Cheney told Democratic senator Patrick Leahy to "fuck yourself" during a dispute on the floor of the Senate in 2004. Even Cheney's boss, George W Bush, was once caught on video describing a journalist as a "major-league asshole".

Biden should remember the words of John Nance Garner, vice-president under Franklin Roosevelt, who said: "The vice-presidency isn't worth a pitcher of warm piss."