In an interview with a virulently anti-Western Russian newspaper, Mr Le Pen, 86, gave credence to conspiracy theories circulating on the internet suggesting that the attack was the work of American or Israeli agents seeking to foment a civil war between Islam and the West.

His comments – only partially retracted in an interview with the French newspaper Le Monde today – provoked outrage amongst French politicians. They will also infuriate Marine Le Pen, his daughter, and successor as leader of the FN, who has been trying to distance the party from her father’s extreme and provocative remarks.

Mr Le Pen stood down as FN leader three years ago but remains President-for-life. He made the comments in an interview withKomsomolskaïa Pravda , a newspaper which had already blamed the United States for the terrorist mayhem in France.