On the accumulation of White House power under the current administration, Ms Clinton said the president and Dick Cheney both had taken actions "beyond any power the Congress would have granted" and – even when congressional authorisation was possible – chosen not to pursue it "as a matter of principle".

"The power grab undertaken by the Bush-Cheney administration has gone much further than any other president and has been sustained for longer," she said. "Other presidents, like Lincoln, have had to take on extraordinary powers but would later go to Congress for either ratification or rejection."

Ms Clinton said the accumulation of executive power had put America into "new territory" because Mr Bush and the vice president had taken the view that were what previously extraordinary powers were now inherent powers that belonged to the White House.

"I think I’m going to have to review everything they’ve done, because I’ve been on the receiving end of that," she said. Ms Clinton stated it was "absolutely" conceivable that, as president, she would give up executive powers in the name of constitutional principle.

"That has to be part of the review I undertake when I get to the White House, and I intend to do that," she said.