A rotten or pocket borough , more formally known as a nomination borough or proprietorial borough , was a parliamentary borough or constituency in England , Great Britain , or the United Kingdom before the Reform Act 1832 , which had a very small electorate and could be used by a patron to gain unrepresentative influence within the unreformed House of Commons . The same terms were used for similar boroughs represented in the 18th-century Parliament of Ireland .
Rotten borough , depopulated election district that retains its original representation. The term was first applied by English parliamentary reformers of the early 19th century to such constituencies maintained by the crown or by an aristocratic patron to control seats in the House of Commons . Just before the passage of the Reform Act of 1832, more than 140 parliamentary seats of a total of 658 were in rotten boroughs, 50 of which had fewer than 50 voters. See also pocket borough .