Michael Crick investigates the impact of the proposed changes in Liverpool and on the Isle of Wight
The Lib Dems would have lost out most if proposed constituency changes had been implemented at the last election, research for Newsnight has suggested.
The party would have lost 12% of seats - seven of 57. Labour would have lost 10% - 25 of 258, and the Tories 4% - 13 of 307, the estimates show.
The research also suggested Wales would have lost 25% of its seats, N Ireland 17%, Scotland 12% and England 6%.
The Democratic Audit study did not assess the impact of Alternative Vote.
The coalition government has announced plans to introduce legislation for a series of electoral reforms.
It wants to hold a referendum next May on changing the Westminster voting system from first past the post to the Alternative Vote (AV), where candidates are ranked in order of preference.
The coalition's Parliamentary Voting System and Constituencies Bill - a key component of the coalition deal between the Conservatives and Lib Dems - also includes proposals to shrink the number of MPs from 650 to 600 and to create constituencies of equal size across the UK.
New constituencies would be set within 5% of a target quota of registered voters.
Labour opposes the proposals, arguing that the constituency changes would benefit the Conservatives at the expense of Labour.
The Conservatives complain the current boundaries require them to win more votes than Labour to gain the same number of MPs, because on average Tory seats have more constituents.
Stuart Wilks-Heeg and Stephen Crone, commissioned by Newsnight, used 2009 Electoral Statistics to estimate what the impact would have been on the parties had the 2010 election taken place with just 600 seats under first-past-the-post rules.
They first calculated how many seats each of the nations would have been entitled to in a 600-seat House of Commons - assuming an average of 76,000 electors per seat.
They estimated such reforms would have left England with 503 constituencies, down by 30; Wales with 30, down by 10; Scotland with 52, down by seven; and Northern Ireland with 15, down by three.
Therefore, Wales would have lost 25% of its seats, Northern Ireland 17%, Scotland 12% and England 6%.
Within England, the researchers calculated the northwest would have lost most seats (7), followed by the West Midlands (5) and Yorkshire and the Humber (4).
The fewest seat reductions were likely to have been in the east of England (1) the East Midlands (2) and the south west (2).
The researchers also estimated the likely impact the changes would have had on party representation.
They found that Labour would have lost out on more seats than any other party - 25 out of 258. This compared to 13 out of 307 for the Conservatives and seven out of 57 for the Lib Dems.
"These estimates suggest that, if the 2010 election had been fought on the basis of 600 seats with equalised electorates, Labour would have lost ground relative to the two other main parties," the researchers concluded.
"As many as half of the 50 seats due to disappear from the Commons could be notionally Labour seats."
But proportionally, the Lib Dems would have been worst off - losing 12% of seats, compared with 10% for Labour and 4% for the Tories.
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