Millions of Labour voters have deserted the party in protest over mass immigration.
A poll reveals that nearly eight in ten former Labour voters support drastic curbs on migrant numbers.
It also shows huge support for sharp cuts in arrivals among those who have remained with the party.
In 1997, some 13.5million voted for Labour, but by the 2010 election that had fallen to 8.6million.
Analysis of the views of some of the five million ‘lost’ Labour voters by YouGov shows 78 per cent want net migration cut to zero.
That policy would mean foreign migrants would be allowed in only to replace people who left – in effect, a one-in-one-out rule.
The YouGov poll, published in Prospect magazine, interviewed thousands of Labour ‘defectors’. Pollsters also found that two-thirds of Labour party loyalists backed zero net migration.
Sir Andrew Green, chairman of the MigrationWatch think tank, said: ‘This is stunning research which is bound to affect Labour’s immigration policies.
‘We will see whether they have the courage to declare a limit on immigration or whether they try to duck this essential issue. The track record so far is not encouraging.’
Ed Miliband signalled this month that he wanted more done to tackle immigration, saying low-skilled immigration into Britain was ‘too high’.
But the Labour leader offered no policy proposals for how he would fix the problem.
Labour’s open-door migration policy led to the largest population explosion in Britain since the Saxon invasion.
Between 1997 and 2010 the foreign-born population of the UK increased by three million, while nearly a million British citizens left the country.
Last year net migration stood at 216,000, down from 252,000 in 2010.
Home Secretary Theresa May has imposed a cap on migrant worker numbers and led a crackdown on family migration and bogus students.