Earlier Mr Johnson had told MPs that plans to merge the Foreign Office and International Development departments were "a big step forward for global Britain".
But while Mr Blunt, a long-term critic of Israel, said he welcomed the merger he said: ''In two weeks' time our ally, Israel, is going to annex elements of the occupied Palestinian territories, a grave breach of international law.
''Surely we must try to divert them from that propect with real sanctions if they breach international law.''