Turnout was 61% in the general election

The index of democratic power, drawn up by the New Economics Foundation (NEF) think tank, urges action to reform the parliamentary electoral system.

The index was calculated using British voters' ability to influence the results of elections from 1954 to 2005.

NEF's Nic Marks said: "The structure of the electoral system is undemocratic and unequivocally unjust."

INDEX OF DEMOCRATIC POWER All Britain's parliamentary constituencies have been assigned an IDP figure The index is designed to show how much of the "fair share of democracy" each seat has The figure is based on a formula involving a seat's population and the likelihood of it changing hands at an election Find out your constituency's IDP on the New Economics Foundation website (see right) If you do not know your constituency name, enter your postcode in our 2005 election results database to find out 2005 election results

He said that because many people feel their vote would not have much influence, they would not bother to vote.

"Urgent action is needed to ensure that the British electorate is given a fair share of democratic power," he said.

The calculations were based on whether a person's vote had the potential to influence who was elected in their constituency.