Andy Sawford, Labour's Prospective Parliamentary Candidate for Corby and East Northamptonshire, said:
"Louise Mensch was obviously struggling to balance being MP for Corby and East Northamptonshire with her family and business commitments. I respect her for the honest way she talked about this and her decision to step down.
"Labour is now looking forward to the campaign ahead, fighting for action on jobs and the economy, supporting our local services which are facing massive cuts and working with local community organisations.
"During the by-election we will focus on the two wasted years of Tory policies that have taken the country back into recession and left Corby suffering job losses in both the public and private sector.
"This will be a tough election for Labour but we are determined to hold this Tory-led Government to account by showing the disastrous impact of its policies on the people of Corby."