In a hard-hitting speech on an issue that is fast becoming the central battleground for next May's general election, British Prime Minister David Cameron suggested on Friday that the UK could leave the European Union if it is prevented from curbing migrant access to welfare.

The Conservative Party leader unveiled a package of reforms aimed at reducing so-called "benefit tourism" - and with it, the flow of migrants into the United Kingdom. Cameron laid out plans to bar foreign jobseekers from claiming benefits such as income and housing support, and for a provision establishing the ability to deport them if they did not find work within six months. Migrants would also be barred from sending child benefit payments abroad, a measure designed to prevent people claiming for children who are not living in the UK.

Cameron also said that Britain must be allowed to withhold welfare or social housing from European migrants for four years after their arrival in Britain.

The measures would "deliver the toughest system on welfare for EU migrants anywhere in Europe," he insisted. Critics of the existing arrangement say that the comparatively generous welfare systems on offer in countries such as Britain and Germany - which has also recently moved to curb benefits for migrants - make them a honeypot destination for citizens from poorer EU states.

But it is a highly contentious issue. Many of the proposed changes will clash with EU legislation, and the European Commission is resolutely opposed to any reforms on the issue. Jean Claude Juncker, the new commission president, last month lambasted Cameron for attempting to "destroy" the European principle of freedom of movement, accusing the British leader of a "historic mistake" on the EU.

Cameron, however, insisted that his proposals were an "absolute requirement," raising the specter of a British departure from the bloc if it is not allowed to set its own rules on welfare for migrants.

If he failed in the renegotiation, Cameron remarked, "Nothing, and I mean nothing, is ruled out."

"We have real concerns. Our concerns are not outlandish or unreasonable," Cameron insisted, adding that the worries were not unique to Britain and that discussions on the issue could not start with a "No."

"Across the European Union, issues of migration are causing real concern and raising real questions," he said. "Can movements on the scale we have seen in recent years always be in the best interests of the EU and wider European solidarity? Can it be in the interests of central and eastern European member states that so many of their brightest and best are drawn away from home when they are needed most?"

Cameron also promised more funds to communities where local services were struggling to cope with the current level of immigration.

Britain is one of a number of European countries that have seen a backlash over the EU principle of free movement, which critics say has led to a pace of immigration into richer countries that is putting a strain on infrastructure and squeezing the job market.

All the major political parties have turned their attention to the issue, in part due to the perceived threat from Nigel Farage's UK Independence Party (UKIP), which has seen growing support for its anti-European and anti-immigration platform.

Supporters of the principle of free movement insist it is good for the British economy and accuse those who oppose unlimited immigration of racism and an insular "Little England" mentality. They say the focus on so-called welfare tourism is a false inflation of a minor problem, accusing politicians of pandering to populist and nationalistic sentiment.

An emotive and often racially-charged issue, the immigration question is stoking divisions not only along political lines but increasingly ones of class. Nowhere was that more evident than in the recent resignation of Emily Thornberry as the Labor opposition's shadow attorney general amid accusations of snobbery towards UKIP supporters.

After UKIP won the Rochester by-election - a special vote triggered by the defection of its member of parliament (MP) from the Conservatives to Farage's party - on November 20, Thornberry tweeted a photograph of a white van parked outside a house adorned with several St George's flags, with the caption "Image from Rochester." The tweet drew a storm of protest, with Thornberry accused of "sneering" at the British working classes.

One Labor MP, Simon Danczuk, said the party had been "hijacked by the north London liberal elite," a nod to the sentiment of many UKIP supporters that the establishment - and the wealthier residents of the capital - is out of touch with the concerns and pressures of everyday people.

For many on that side of the divide, Cameron's proposals did not go far enough, falling short of a demand for immigration quotas as desired by UKIP and some Conservatives.

Steven Woolfe, a UKIP member of the European Parliament, insisted the prime minister had failed the British people on the issue, pointing to figures released on Thursday that showed net migration of 260,000 in the year to June - an increase of 78,000 on the previous year.

"The fact remains that as a country we cannot control the quantity and quality of migration into the UK, whilst we remain a borderless country inside of the EU," Woolfe said in a statement.

But others raised concern about the tone of the rhetoric in the immigration debate. Dan Hodges, a columnist for the conservative-leaning Telegraph newspaper, conjured the ghost of Enoch Powell and his notorious "Rivers of Blood" speech of 1968, in which the then-member of the opposition shadow cabinet predicted that immigration would herald a catastrophe for Britain.

Hodges described the effort of politicians clambering to out-tough each other on the issue as an "anti-immigration arms race" prompted by the challenge from Farage.

Cameron had not gone as far as Powell, he wrote. "But is that what it will take before someone finally says 'enough'? Only when Cameron fully evokes chilling images of a foaming River Tiber will people acknowledge, 'OK, this debate is getting out of hand now'?"

"It seems no one is prepared to call a halt to the anti-immigration arms race," Hodges went on. "But we can't afford to wait for the ghost of Enoch Powell to return before they do."