Regaining control over UK borders would be a "valuable defensive tool" in protecting Britain from future terrorist attacks, a justice minister will warn.
Dominic Raab will say current EU rules mean UK intelligence agencies are powerless to bar EU nationals believed to be linked to terrorism from entering the UK.
He believes the European Court of Justice has made it "increasingly difficult" for the UK to deal with the risk of free movement.
The Eurosceptic minister is expected to raise fears about UK security during a speech to Vote Leave supporters in central London on Wednesday.
He is expected to say: "Crucially, for UK intelligence agencies, we cannot bar individuals on whom we have sketchy intelligence but reason to believe may be linked to terrorist related or other serious criminal activity. Or who may have done something which gives rise to questions, such as visiting Syria, without a clear or credible reason.
"In most countries outside the EU, you can bet that individuals flagged in this way would not waltz through passport control without these doubts or question marks being answered or assuaged.
He will add: "EU rules set the bar for taking meaningful action impossibly high which means we effectively have to give a free pass into Britain to those coming from the EU.
"It massively increases the pool of people that need to be monitored by the intelligence agencies.
"The numbers involved make it exponentially harder for them to sift out those presenting a credible and current danger. Those individuals who should attract the closest surveillance.
"And that means we are importing risk and stretching our capacity to cope with it on a worrying scale."
Mr Raab, who has previously accused the In campaign of scaremongering and using fear tactics, will warn terrorists believed to be behind the Paris and Brussels attacks were able to travel across Europe because of the principle of free movement.
He will say: "It is too early to accurately assess the extent to which borderless travel facilitated those involved in the Brussels attacks.
"But, it is undeniable that regaining control over our borders would be a valuable defensive tool in protecting Britain from future terrorist attacks."
He will add that the EU will be desperate to co-operate with the UK in the event of a Brexit because the country has the largest DNA database and the best intelligence networks in Europe.
"To suggest the EU would be anything other than desperate to retain UK co-operation if we left is as ridiculous as saying German car manufacturers would be relaxed about their ability to continue exporting cars to British consumers."
Will Straw, executive director of Britain Stronger In Europe, accused the Leave campaign of being "misleading" and said the authorities can deport suspected criminals who enter the UK using a European Arrest Warrant.
He said: "The Leave campaigns have clearly given up on having an honest debate and are being deliberately misleading.
"What they won't admit to voters is that leaving Europe could see the UK border move from Calais to Dover. It would mean our intelligence services wouldn't have access to databases of criminals' DNA. It would mean an end to our invaluable use of the European Arrest Warrant.
"That's why the weight of opinion in the UK and within the international intelligence community - including six former Home Secretaries, a former immigration minister, the former Director of Public Prosecutions, the British Director of Europol and the former head of the UK Border Force - is behind Britain staying in the EU."
Nick Herbert, chairman of Conservatives In and a former policing and criminal justice minister said it was "irresponsible" for Brexit campaigners to suggest the UK could not turn away people at the border.
He said: "They are willing to place their ideological opposition to any EU co-operation ahead of effective security measures.
"The UK is outside Europe's passport-free Schengen area, we have border controls and checks, and we can and do turn away people who pose a threat to our country.
"It is simply irresponsible to suggest otherwise."