Europeans will have to prove they are “genuinely seeking employment” to claim UK jobless benefits for more than six months, David Cameron has said.
The prime minister said it was among measures to ensure people came to the UK “for the right reasons” after it became a “soft touch” under Labour.
But Bulgaria’s UK ambassador said the UK’s rules were already seen in his country as “very restrictive”.
Labour warned against an “arms race on immigration rhetoric”.
Migrants from the European Economic Area – the EU member states plus Iceland, Liechtenstein and Norway – currently have to show they have a “reasonable chance” of finding a job to receive unemployment benefit for more than six months.
Downing Street said they would now face a more rigorous test to assess whether they had a “realistic prospect” of getting a job, with the ability to speak English one of the criteria.
In his speech in Ipswich, the prime minister said there were “concerns, deeply held, that some people might be able to come and take advantage of our generosity without making a proper contribution to our country”.
Immigrants have been coming to Ipswich for centuries. But where once they came for work and trade, David Cameron thinks too many are coming now to claim benefits.
That is why he came to Suffolk today to set out his latest plans to dissuade all but what he called the “brightest and the best” migrants from coming here.
He and his fellow party leaders are now in a competition to see which of them can come up with the toughest policy on immigration.
The aim is to reassure voters and prevent too many of them backing UKIP.
The problem for Mr Cameron is that many of his proposals tackle only part of the problem.
The truth is that his room for manoeuvre is limited by EU freedom of movement rules.
There is also the risk that in this immigration arms race, the three largest parties cancel each out and the public end up more confused than reassured.
“These concerns are not just legitimate; they are right and it is a fundamental duty of every mainstream politician to address them.”
No 10 was unable to give any figures on the scale, cost and numbers of so-called benefit tourists, although Department for Work and Pensions figures suggest 17% of working-age UK nationals claim a benefit, compared with 7% of working age non-UK nationals.
Transitional restrictions on Bulgarians and Romanians working in the UK are due to be relaxed next year.
Since the countries joined the European Union in 2007, their peoples have been able to come to the UK to live and have been able to take jobs either via a work permit system, or by being self-employed, or in a variety of jobs from domestic work to seasonal agriculture.
According to the Office for National Statistics, in July 2012 there were 94,000 Romanians and 47,000 Bulgarians resident in the UK.
The end of existing controls will give those who want to work in the UK the same rights for welfare and NHS care as foreign nationals from the other 24 EU nations.