French President Nicolas Sarkozy has said there are too many foreigners in France and the system for integrating them is "working worse and worse".
In a TV debate, Mr Sarkozy defended his plan to almost halve the number of new arrivals if re-elected next month.
Mr Sarkozy is trailing in the opinion polls behind the Socialist candidate Francois Hollande.
He is also competing for conservative voters with the far-right National Front party led by Marine le Pen.
The president said while immigration could be a boon for France, it needed to be controlled more tightly through tougher qualification rules for residency.
Mr Sarkozy, whose father was a Hungarian immigrant, also said he wanted to restrict some benefit payments to immigrants who had been in the country for 10 years.
Tough new rules
He has often made controversial comments on race and immigration issues, sharply dividing opinion in France.
In 2005, just before the Paris riots, he described young delinquents in the Paris suburbs as "racaille", meaning rabble.
He has said that if re-elected, he will reduce the number of immigrants to France from 180,000 a year to 100,000 and introduce tighter controls on access to welfare benefits.
As president, Mr Sarkozy has already pushed through tough new immigration rules, including the controversial deportation of Roma (Gypsies).
On Tuesday, Prime Minister Francois Fillon caused dismay among Muslim and Jewish groups by suggesting the religious slaughter of animals was out of date.
The controversy started when a TV documentary said last month that all the abattoirs in Paris region only produced halal meat.
So far the election campaign seems to have made relatively little impact on voters.
The latest opinion poll published on Tuesday by CSA showed the Socialist leader Francois Hollande widening his lead over President Sarkozy for the 22 April vote.
It also suggested that the Socialist leader would win decisively by 54% to 46% in a second round of voting on 6 May.