Murderers, terrorists and kidnappers from countries like Turkey could flock to Britain if it remains in the European Union, Leave campaigners have claimed.
The NHS will also be put under huge strain if Turkey joins the bloc, costing maternity services nearly £400 million in 10 years, armed forces minister Penny Mordaunt warned.
Leave campaigners claimed that allowing countries on the path to EU membership to join was "dangerous" and made the country "less safe".
Accession of Turkey, Albania, Montenegro, Serbia and Macedonia will bring 12,726,000 guns into the single market, Vote Leave said.
Britain will be "less safe" by remaining in the EU
Vote Leave also pointed to UN figures showing there were more than twice as many criminal prosecutions in Turkey as in the UK in 2013 - 3.5 million compared with 1.5 million.
And the Brexit camp used Romanian and Bulgarian migration rates to predict that around 142,000 Turkish citizens a year could head to the UK if the country gains full EU membership.
High Turkish birth rates - 17.4 per 1,000 people compared to 12.1 in Britain in 2014 - could cost the NHS £400 million in maternity services in a decade, it claims.
Turkey not joining EU "any time soon"
But Conservative former foreign secretary Sir Malcolm Rifkind insisted Turkey would not be joining the EU "any time soon".
He said: "Vote Leave are desperate to avoid experts' warnings that leaving Europe would send Britain back to recession, and so are making arguments that are absurd and untrue.
"Even Boris Johnson has said that Turkey joining the EU is 'simply not on the cards'.
"Turkey simply will not join the EU any time soon. In 30 years of negotiations, they have completed just one of the 35 tests they need to fulfill to apply to join".
Similarly, shadow foreign secretary Hilary Benn accused the Leave campaign of trying to "scare" voters.
"The Leave campaign should stop trying to mislead and scare voters," he said.
"The fact is that Turkey joining the EU is a very distant prospect".