The Prime Minister will today announce that from November the period of time that European migrants can claim benefits will be halved.
Mr Cameron will say the new measures are designed to ensure those who come to the UK do so for the right reasons.
They are announced just 24 hours after reports that Labour think popular support for the arch-eurosceptic Ukip could be enough to force Mr Cameron out of Downing Street.
Yesterday it emerged that Labour believe Ed Miliband will win the race to No 10 if Ukip gets 9% of the vote in the election.
That would deprive the Conservatives of enough votes to ensure Mr Cameron's party does not win the election, according to opposition strategists.
Ukip are currently on about 13% in the polls, but took a whopping 27% of the vote across the UK at the European elections earlier this year. The party also pulled off a surprise win in Scotland, gaining their first ever elected politician north of the Border when they beat the SNP to claim their sixth MEP.
The Conservative-Liberal Democrat Government is facing increasing pressure over immigration, amid signs it will fail in its target to cut net figures to the tens of thousands by the end of this parliament.
In January, Coalition ministers brought in new rules that meant European migrants had to wait three months before they could claim out-of-work benefits.
Once they become eligible they are also able to receive help only for a maximum of six months, unless they can prove they have very clear job prospects. Today the Prime Minister will announce a cut in that period to three months.
Applicable to Jobseeker's Allowance, Child Tax Credit and Child Benefit, the new rules will come into force in November.
The Prime Minister will also highlight a range of other measures that have come into force recently, including new powers to revoke the driving licences of illegal immigrants.
In a newspaper article today, Mr Cameron says: "Under Labour, 2.5 million more people came to this country than left.
"There was a failed points system, which allowed so-called 'highly-skilled' workers to come here for up to three years to look for work - and often they ended up stacking shelves.
"There was an increasingly generous, no-questions-asked welfare system, that drew migrants to Britain for the wrong reasons. And unforgivably, while we had the highest rates of migration in our modern history, we also had well over five million people of working age on out-of-work benefits."
"We're ... making sure people come for the right reasons - which has meant addressing the magnetic pull of Britain's benefits system."
Yvette Cooper, Labour's shadow home secretary, accused the Prime Minister of offering more talk than action on immigration.
"Behind the rhetoric the true picture of this Government on immigration is one of failure, with net migration going up, despite David Cameron's promise to get it down to the tens of thousands," she said.
"The Government should get a grip and finally implement Labour's proposals to stop the undercutting of wages and jobs for local workers by the exploitation of low-skilled migrant labour, including banning recruitment agencies that only hire foreign workers and pressing for stronger controls in Europe."