In 2001, when the Bush administration was trying to win congressional authority to negotiate new trade agreements, two of the leading figures in the debate in Congress had a brief encounter that may come back to haunt the White House.

Bill Thomas, the powerful Republican head of the House ways and means committee, was approached by Sander Levin, then the top Democrat in the committee on trade issues and a supporter of most of the big free trade initiatives of the past decade. When Mr Levin suggested a negotiation on the substance of the bill particularly on the issue of how labour standards should be incorporated into new trade deals Mr Thomas fired back: “I consider you part of the enemy on this issue.”