A Daily Telegraph/YouGov survey shows that it is the top concern that people want an incoming Conservative government to deal with.
Fifty-two per cent said they wanted a Tory administration to reduce immigration.
This week immigration figures revealed that one in nine people living in Britain was born overseas, highlighting a significant change in population make-up under Labour.
There were 6.5 million people born abroad who were resident in the UK in June 2008. This represented a rise of 290,000 on the previous year and 1.2 million since 2004.
The issue of foreign workers sparked strike action across the country when a refinery in Lincolnshire employed Italian workers to complete a contract, instead of using UK workers. Unions accused Gordon Brown of going back on his commitment to ensure there were "British jobs for British workers."
The issue caused consternation among many Labour MPs who watched their traditional supporters protesting so strongly against the Prime Minister.
Labour ministers are aware that immigration is now a problem for them among their core voters. Hazel Blears, the Communities Secretary, recently said that the "white working class" feels ignored over the issue.
In today's poll it also comes top of the list of concerns among Labour voters with 42 per cent saying it should be cut compared to 62 per cent of Conservative backers.
Reducing the power soft the European Union is second and providing more to help families is third.
The poll also shows a comfortable lead for the Tories over Labour. The Conservatives are on 41 per cent, down two on last month, and Labour on 31, down one point on January's survey. The Liberal Democrats polled 15 per cent, down one.
That result would only, however, give Mr Cameron a Commons majority of 38. He and his party strategists are determined to land a sizable majority and capitalise on the Government's unpopularity.
When asked who would make the better Prime Minister, 25 per cent said Mr Brown, down two, and 33 per cent Mr Cameron, also down two.
There is more bad news for the Prime Minister with the finding that only 14 per cent believe the Government's measures to tackle the recession are working. Lord Mandelson, the Business Secretary, admitted this month that Labour needed to hold its nerve because the effect of its recession measures were not yet being felt.
The arrival of Ken Clarke as Lord Mandelson's opposite number has had an immediate impact. When asked who would make a better Business Secretary, 48 per cent said Mr Clarke and only 17 per cent favoured Lord Mandelson, who like Mr Clarke was brought back to bolster his party's front bench team.
One recent poll put the Conservatives 20 points ahead.
Mr Brown's own popularity also continues to decline. Sixty-five per cent of voters are dissatisfied with him as Prime Minister, up two from last month, and only 25 per cent are satisfied, down two.
When asked whether Mr Cameron was proving a good leader of the Conservative party 46 per cent said yes, the same as last month.
The Tories have also emerged as the party more trusted to get the country out of the present crisis  reversing the position of last autumn. Then Mr Brown's assured handling of the crisis saw an increase in his personal standing and an improvement in Labour's poll ratings.
But now 35 per cent say the Tories are more trusted to deal with the crisis and only 28 per cent Labour.