Any action taken by either a Member of Parliament or a member of the public which obstructs or impedes either Parliament in the performance of its functions, or its members or staff in the performance of their duties, is a contempt of Parliament.
Examples of contempt include giving false evidence to a parliamentary committee, threatening a Member of Parliament, forging documents and attempting to bribe members.
The Commons has the power to order anyone who has committed a contempt of Parliament to appear at the Bar of the House and to punish the offender.
If the offence has been committed by an MP he or she may be suspended or expelled.
For example, Labour MP Keith Vaz was suspended from the Commons for one month after being accused of "a contempt of the House" by the Commons Standards and Priveleges Committee in 2002.
But under current rules, a member of the House of Lords cannot have his or her peerage withdrawn.