David Cameron would be swept into 10 Downing Street with a Commons majority of 218 if the Norwich North result was repeated across the country at the next General Election, Press Association analysis shows.
The Tories would have 434 MPs, with Labour on 107, Liberal Democrats 79 and others 30.
It is assumed that there is no change to figures for the SNP, Plaid Cymru and minor party seats.
The Buckingham constituency of Speaker John Bercow is included with the Conservatives, and Glasgow North East, where there is a by-election pending, with Labour.
The calculations are based on new boundaries - coming in at the next General Election - using estimates by Professors Colin Rallings and Michael Thrasher, of Plymouth University, on how voting in constituencies would have divided if the changes had been in force in 2005.