Parliamentary privilege, also known as absolute privilege, is a legal mechanism employed within the legislative bodies of countries whose constitutions are based on the Westminster system. In other legislatures, a similar mechanism is known as parliamentary immunity.In the United Kingdom, it allows members of the House of Lords and House of Commons to speak freely before those houses without fear of legal action on the grounds of slander. It also means while a member is within the grounds of the Palace of Westminster he/she cannot be arrested on civil matters; there is no immunity from arrest on criminal grounds. A consequence of the privilege of free speech is that legislators in Westminster systems are forbidden by conventions of their House from uttering certain words, such as "liar" (see unparliamentary language).
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An absolute defence to an otherwise defamatory statement because of the venue or context which the statement was made. - (read more on Absolute Privilege)