Parliamentary privilege grants certain legal immunities for Members of both Houses which allow them to perform their duties without interference from outside the House. The privileges are: Freedom of speech, freedom from arrest (on civil matters), freedom of access to the sovereign and that 'the most favourable construction should be placed on all the Houses's proceedings'. Members are immune from legal action in terms of slander but must adhere to the principles of parliamentary language.
Further information on this subject can be found from the following link.
Standards and Privileges Committee