"Nobody was ready. We're in a situation of improvisation," Sapin told reporters when asked about British Finance Minister Philip Hammond's veiled threat to use corporate tax as a form of leverage in Brexit negotiations.

"All of this shows how helpless the British government is in the face of a situation that some of them didn't want," Sapin added.

France would welcome more clarity and would like Article 50 of the Lisbon Treaty to be triggered as soon as possible, he said.

(Reporting by Michel Rose; Editing by Richard Balmforth)