It was a rare breach of the protocol that governs ritualistic events in the Capitol. In an angry and very audible outburst, Representative Joe Wilson, Republican of South Carolina, interrupted US President Obama’s speech on Wednesday night with a shout of “You lie!”

His eruption — in response to Obama’s statement that Democratic health proposals would not cover illegal immigrants — stunned members of both parties in the House chamber. Democrats said it showed lack of respect for the office of the presidency and was reminiscent of Republican disruptions at recent public forums on health care.

“I was embarrassed for the chamber and a Congress I love,” Vice-President Joseph Biden said on Thursday on ABC’s Good Morning America. He said that he had not spoken to President Obama since the speech. But, “knowing the President, I’m sure he accepted the apology”.

After the speech, Rahm Emanuel, the White House Chief of Staff, said he immediately approached senior Republican lawmakers to encourage them to identify the heckler and urge him to issue an apology quickly.

Wilson later apologised for his “lack of civility” during the speech but defended the objection.