The Clinton campaign on Monday accused Barack Obama of plagiarism after the discovery that the senator from Illinois had lifted a passage from a speech given by Deval Patrick, the governor of Massachusetts, two years ago.

In an attack designed to remind people of Joe Biden’s withdrawal from the 1988 presidential campaign after his uncredited use of passages from Neil Kinnock, leader of the Labour party opposition in the UK, the Clinton campaign said it raised “fundamental questions” about the integrity of Mr Obama’s campaign.