By Alex Gangitano Follow @alexgangitano
The full scale of immigration's impact on Labour's support was revealed in a new survey today, ahead of a planned Ed Miliband speech on the issue.
A YouGov poll revealed up to 78% of supporters who left Labour wanted drastic cuts in migrant numbers.
This research was "bound to affect Labour's immigration policies," said Andrew Green, chairman of think tank Migration Watch.
Many lost voters support extremely restrictive immigration policies which would cut net migration down to zero and only allow in migrants if someone left the country.
Between 1997 and 2010, Labour lost five million voters, although factors such as Gordon Brown's unpopularity and Britain's economic decline will also have affected the party's performance.
In his conference speech last month Ed Miliband said low-skilled immigration into Britain was too high and stressed his desire to do more to tackle immigration.
The Labour leader is expected to make a speech on the issue in the next few weeks but he faces a difficult balancing act in pleasing the party's white working class supporters and progressive middle-class members, who are generally more sympathetic to immigration.