EU migrants are coming to the UK because of higher wages and a lack of a jobs in the eurozone - but there is no evidence of "benefits tourism", according to new analysis.

Six countries - Poland, Romania, Spain, Italy, Hungary and Portugal - accounted for an 80% of the increase in EU migrants living in Britain in recent years.

The report, by the Migration Observatory, also said that any evidence of migrants travelling to the UK for "benefit tourism" remained unproven.

Between 2011 and 2015, the total number of EU-born migrants living the UK increased by 696,000 to 3.277 million.

The UK's apparent attractiveness for EU citizens has been the cause of fevered debate ahead of the EU referendum. Brexit campaigners have claimed that leaving the EU will allow the UK to reclaim control of its borders and reduce immigration, while others have said there is no way of knowing what impact a British exit would have.

(Migration Observatory (Migration Observatory)

The Observatory, based at Oxford University, concluded there was no single "pull" factor bringing EU migrants to Britain.

Researchers said some of the factors encouraging migration to the UK were permanent, such as the attraction of the English language, while others have the potential to change over time.

For example, economic factors like high unemployment in southern Europe and lower wages in Eastern Europe are likely to be key drivers of recent migration.

But it found no clear evidence that welfare benefits were the "unnatural draw" for people to move to Britain.

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EU migrants were more likely than British citizens to be in-work and childless, meaning they did not claim job seeker's allowance or benefits aimed at people with children. But they were slightly more likely to claim in-work benefits such as tax credits - 12% of EU-born workers compared to 10% British-born workers.

The findings suggest that David Cameron's "emergency brake", secured during his EU renegotiation, limiting in-work benefits for EU migrants for four years, could make little difference to the numbers coming to the UK. But it also appears to undermine claims by pro-Brexit campaigners that EU migrants are attracted to the UK because of generous welfare benefits.

Those who want to leave the EU say Britain must regain control of its borders so it can choose whether workers from low-wage countries, such as Romania, can come here to work. Remain supporters counter that such migration has boosted the UK's economy, and that Britain would probably have to agree to freedom of movement as a price of remaining in the single market.

(Migration Observatory (Migration Observatory)

Madeleine Sumption, director of the Migration Observatory, said: "There is no single factor driving high levels of EU migration in recent years.

"Some drivers are likely to remain in place for some years, such as the relatively low wages in new EU member states, particularly Romania.

"Others could potentially dissipate more quickly, like high unemployment in Spain."

The commentary argued it is too early to tell how the introduction of the National Living Wage will affect migration, saying that while it may increase the financial advantage of moving to the UK from a lower-income EU country, it could also push UK employers to rely less on low-wage workers, including those from the EU.

Ms Sumption added: "Despite recent debates about the role of UK policies like welfare benefits or the minimum wage in driving migration, migration may respond more to factors that governments don't directly control, like demographics and economic growth in other EU countries."

The latest official data show estimated net migration of EU citizens to the UK was 172,000 in the year ending September.