Nigel Farage warned on Friday Britain was "far less safe" and exposed to Cologne-style sex attacks because of open-door immigration.
Speaking in London, the Ukip leader said it would be "impossible" for Britain to control immigration if it remains an EU member state.
He added that he believed 5,000 jihadis posing as migrants had made it to Europe via Greece over the last 18 months.
Mr Farage argued whether "it is any wonder" the country also faces a housing crisis, that green-belt land is threatened, and the burden to find more primary school places is growing.
Meanwhile Conservative MP and Remain campaigner Justine Greening warned a potential Brexit would be equivalent to "walking away from being a voice around the table where decisions affect us".
Leave advocate Mr Farage also accused the Remain campaign of unleashing a "remorseless torrent of propaganda" scaring the UK population before the EU referendum on June 23.
US President Barack Obama's recent trip to the UK was also lambasted, with Mr Farage accusing him of parroting the Remain line.
Mr Farage said the current trade deal Britain has as an EU member is "rotten", despite attempts to negotiate.
We need to be much more assertive in making the economic point that Britain will be better off outside the EU, whatever those negotiations lead to.
In terms of the NHS, Mr Farage said it was "rotten" that Britain paid out £6.2 billion to European hospitals, while £405 million came the other way.
He also added that immigration had caused the wages of ordinary UK citizens to decrease in value 10% since 2008.
Mr Farage reiterated his desire to implement an Australian-style points system to determine immigration.
We don't want to discriminate against them, because they're from India or New Zealand in favour of Romania and Bulgaria - we should be open to the world.
Mr Farage added that German Chancellor Angela Merkel had made the "worst decision" of any western politician since 1945 in her vow to take in "unlimited numbers" of migrants.
Speaking of the Cologne sex attacks, he said: "If we are prepared to accept unlimited numbers of young males from counties and cultures where women are, at best, second class citizens, then frankly what do you expect.
"I do not want those men who were outside of Cologne train station to have one of these [British passport] in a few short years and to be able to come to this country".