Following their review of parliamentary representation in Lancashire leading up to the 2010 United Kingdom general election the Boundary Commission for England created a new seat of Wyre and Preston North in the central part of the county, which caused "knock-on" effects elsewhere. Chorley constituency was one of the largest in electorate at the start of the review, which was a factor in the alterations to both its own composition and the changes to surrounding constituencies. These changes took away from the seat all the areas to the west of the M6 motorway, namely Croston, Eccleston, Bretherton and Mawdesley. These move to South Ribble.