LONDON (Reuters) - Deadly militant attacks in Paris and a string of New Year’s Eve sex assaults in Cologne have increased the need for Britain to leave the European Union, one of the leading ‘Out’ campaigners said on Saturday, citing the need to control national borders.

The leader of the United Kingdom Independence Party (UKIP), Nigel Farage, listens during a Leave.EU campaign news conference in central London, Britain November 18, 2015. REUTERS/Stefan Wermuth

To loud applause, Nigel Farage, the leader of the UK Independence Party, told a Grassroots Out campaign event that Europe’s policy of taking in migrants with few checks had endangered the lives of those living in the 28-member bloc.

British Prime Minister David Cameron has promised to hold a referendum on Britain’s EU membership, with a vote expected to take place later this year and polls showing the outcome is likely to be close.

“I’m a great believer of helping those around the world in need but it’s time to put the interests of men and women and our communities first and we only do that by taking back control,” Farage said.

For years the face of Euroscepticism in Britain, Farage failed to win a national parliamentary seat in the 2015 election but is expected to take a leading role in the campaign for a Brexit, or British exit from the EU.

On Saturday he noted that two of the men who killed 130 people in Paris in November had posed as migrants to enter the EU. Those men accused of groping and assaulting women on New Year’s Eve in Cologne would, he said, have European passports in a few years and be able to enter Britain.

Police have blamed the assaults on migrants, mainly from North Africa.

“It’s now even more serious,” he told the audience of 2,000 people at the cross-party event in Kettering, central England. “The best way to insure ourselves against future terrorism is to take back control of our borders.

“The European Union has made a massive, massive error with its open door policy to anyone that wants to come. To see what was happening with 1,000 young men in public sexually molesting women in the street was a very great shock.”

Farage was joined on the stage by Britain’s former defence secretary Liam Fox from Cameron’s ruling Conservative party who is also campaigning for an exit.