Tory leader vows to crack down on 'benefits tourism'

European migrants could have their access to the welfare state limited, David Cameron said yesterday as he sought to appease eurosceptics in his own party and the increasing numbers of voters won over by Ukip's anti-EU rhetoric.

His attack on so-called "benefits tourism" came as the five-year-old quotas limiting the number of people from Bulgaria and Romania, which joined the EU in 2007, to work and live in Britain are set to expire. That could lead to thousands of workers from those two countries setting off to wealthier parts of Europe in search of jobs. Mr Cameron is due to make a major speech on Europe later this month and yesterday he gave his clearest indication yet that it will include some kind of commitment, in certain circumstances, to a referendum on Britain's future in the EU.

Rather than offer the simple choice of staying in or leaving the EU, which is what many right-wing Tory MPs advocate, Mr Cameron is hoping he can negotiate a change in EU rules that will reduce the power of Brussels and increase that of the Westminster government, and then put the new conditions to a popular vote.

Part of his strategy is to convince the public that he can wrest concessions out of the EU. The Tory chairman, Grant Shapps, came close to saying yesterday that Mr Cameron is more anti-EU than Margaret Thatcher was. Asked by the BBC to compare the two, Mr Shapps praised Mr Cameron as "the only ever British Prime Minister to veto a European treaty". He added: "She never vetoed a treaty."

Mr Cameron told BBC's Andrew Marr: "Should we look at arguments about should it be harder for people to come and live in Britain and claim benefits? Yes, frankly, we should – so there are areas even in the free movement of people where we might want to make changes."

Aides were unable to give any detail yesterday of how he would set about preventing EU immigrants who have come to the UK legally from qualifying for benefits, though they said the Home Office is seeking co-operation on clamping down on bogus marriages that give non-EU citizens access to the welfare state.

But Labour's shadow Foreign Secretary, Douglas Alexander, warned: "Announcing an in-out referendum half-way through this Parliament, to take place half-way through the next, could risk seven years of economic uncertainty, threatening inward investment. Simply presenting a shopping list backed up by a threat of exit will undermine our ability to shape and lead the broader project."