LONDON, Dec 2 (Reuters) - The European Union should amend its derivatives trading rules to avoid harming its own financial sector after Britain fully leaves the bloc at the end of December, France’s top securities regulator said on Wednesday. Robert Ophele, chair of France’s AMF markets watchdog, said the bloc’s derivatives trading rules need adjusting to avoid penalising branches of EU banks that trade in London. (Reporting by Huw Jones; Editing by Jan Harvey)