The growth of the constituency role of MPs has been well documented since the 1960s, in particular the focus on casework. There are clear conventions that MPs should represent all their constituents and should not purport to represent other constituencies. Recent research indicates that these rules are under strain with the advent of devolution and the use of IT such as databases, emails and blogs. More generous allowances enable MPs to employ greater numbers of personal staff to process constituency casework. Parties favour this development, as simultaneously assisting with the permanent campaign and removing potential dissent from Parliament. 

http://www3.interscience.wiley.com/journal/118648119/abstract?CRETRY=1&SRETRY=0