Barack Obama yesterday weighed into the debate over healthcare reform by making his most impassioned case so far to extend universal healthcare coverage to the 47m US citizens who lack it.

Mr Obama's intervention, which came in a speech to the American Medical Association, whose opposition was critical in shooting down Bill Clinton's attempted reform in 1994, comes at a critical stage in the congressional debate which is set to dominate the legislative agenda for the rest of the year.

Mr Obama, who has said healthcare reform is his number one domestic priority, robustly defended his plan to include a public option among the competing healthcare plans. Opponents, including many doctors represented by the AMA as well as private health insurance companies, fear a public option would be a first step on the road to “socialised medicine”.