This is a list of the 646 previous constituencies of the United Kingdom parliament. There are 650 in the 2010 election constituencies currently represented in the House of Commons of the Parliament of the United Kingdom, as at the 2005 general election. Each constituency is represented by a single Member of Parliament (MP). The average constituency size is approximately 74,000 registered voters, but they vary in size from the smallest (Na h-Eileanan an Iar at 22,200 voters) to the largest (the Isle of Wight at approximately 110,000 voters). A constituency has no physical size restrictions.