Row over 'EU criminals in UK' claim
EU exit campaigners have released a list of 50 foreign criminals they say have been allowed into the UK because of freedom of movement rules.
Vote Leave says its list of the 50 "most dangerous" EU citizens includes 45 who "went on to commit serious offences in the UK, including murder and rape".
In campaigners said the dossier was "scaremongering of the worst kind".
The Home Office said the UK was "safer" by being inside the European Union.
The two sides in the EU referendum debate have been trading blows over security issues, with debate intensifying following last week's Brussels attacks.
BBC assistant political editor Norman Smith said the leave campaign was trying to make security its big issue.
"In a way it is their own 'Project Fear'," he said, referencing the criticism levelled at the Remain campaign.
"They are trying to raise concerns about our personal safety and they view it as the counterweight to the Remain side's use of the economic arguments."
The in-out vote on the UK's EU membership takes place on 23 June.
Releasing the document on Tuesday, Vote Leave - one of the groups vying for an EU exit - said instead of refusing criminals entry into the UK, Britain had allowed EU judges to "hang out a welcome sign"
The list includes Latvian Arnis Zalkalns who is suspected of killing London schoolgirl Alice Gross in 2014. The builder, who had been convicted of murdering his wife in Latvia in 1998, later killed himself.
Under current rules, countries are entitled to consult previous police records but criminal convictions alone are not grounds for restricting the right to free movement.
Vote Leave said EU law did not require other EU countries to inform the UK of the criminal records of their citizens.
Chief executive Matthew Elliott said EU membership meant Britain had "lost control of our borders".
"Free movement of people has created free movement of criminals making the UK less safe and less secure. We've allowed EU judges to hang out a welcome sign to individuals the public would rightly expect never to be allowed into the UK," he said.
But Lucy Thomas, from pro-EU campaign group Britain Stronger In Europe, said: "This is scaremongering of the worst kind, particularly as Vote Leave accept that the alternatives to EU membership would include some free movement."
She added: "British security is stronger as part of the European Union, and leaving would put our security at risk."
Home Office Minister James Brokenshire said by being in the EU the UK was able to tackle cross-border crime, saying it had refused entry to almost 6,000 European Economic Area nationals since 2010.
He said the European Arrest Warrant had enabled people fleeing crimes in the UK to be brought to justice and said a vote to leave the EU "would bring inevitable uncertainty" in the fight against criminals "on the lookout for weakness and vulnerability".