 Because Privy Counsellors are bound by oath to keep matters discussed at Council meetings secret , the appointment of the Leaders of Opposition Parties as Privy Counsellors allows the Government to share confidential information with them " on Privy Council terms " . This usually only happens in special circumstances , such as in matters of national security . For example , Tony Blair met Iain Duncan Smith ( then Leader of HM Opposition ) and Charles Kennedy ( then Leader of the Liberal Democrats ) , " on Privy Council terms " to discuss the evidence for Iraq 's weapons of mass destruction . 
