The former Liberal Democrat leader insisted opting out of the European Union’s police database Europol after Brexit would be a mistake, despite security chiefs saying the UK contributes more than to the database than its fellow European nations.
Asked on the BBC’s Today Programme how Brexit would make Britain less safe, Mr Clegg said: “I think the thing to remember is these days anti-terror operations and indeed policing against criminal gangs is principally an intelligence-led and database activity.
“This new database which we gained across to in April 2015 is by far the largest and most sophisticated of its kind.
“We use it, check it 16 times a second, 53 people are detained and questioned under anti-terrorism laws at ports and airports every day by use of this database.
Nick Clegg claimed Theresa May’s Brexit plan is putting the UK at risk
“Because what it includes is, from all of the countries in Europe, a list of all those people who are a subject of concern or suspension from police authorise across the whole of the Continent.
“It is a devastatingly effective crime fighting and anti-terrorism tool but here is the key thing – of course you can’t upload that data onto that database unless you abide by European Union data protection privacy laws and if you don’t abide by those, which is what Theresa May has said, we don’t have access to the database.”
The pro-EU politician accused Theresa May of having created a dilemma for the UK’s security as she pledged to end ECJ rule after Brexit.
Mr Clegg said: “There is a huge difference between saying we want a deal and making a deal possible and this is where I think the Conservatives need to stop, dare I say it, patronising people… Unless they’ve got concrete answers.
“We were told, weren’t we, by Theresa May that this General Election was about Brexit. I think we now need to move beyond cliches to actually coming up with concrete answers to these dilemmas.
I think we now need to move beyond cliches to actually coming up with concrete answers
Get Quotes on Home Insurance
“By the way, which are manufactured exclusively by the Conservatives.
“They could have said that they were going to find a way of abiding by rulings of the European Court of Justice as they apply in these areas, but they haven’t.”
Over the weekend, Mr Clegg also said: "Theresa May's extreme approach to Brexit will have the direct consequence of severing our ties to a fantastically useful weapon in our armoury against terrorism.
"By refusing to accept a role for the European Court of Justice in policing this European-wide database, she has ruled out our future participation it.
"It is hard to overstate the importance of this database. We check it 16 times a second, looking for security threats that have been flagged to us by other European countries. And we use it to tell other countries to stop and question people who we think are potential terrorists.
Snap election 2017: The pictures politicians may not want you to see Sat, May 27, 2017
Protests, fights and daleks, it's all happening as the politicians hit the campaign trail for the snap election
PA 1 of 48
Jeremy Corbyn during a visit to Hackney Marshes Football Pitches, to highlight Labour's manifesto commitment to ensure 5% of the Premier League's television rights income is diverted to the grassroots game, during a General Election campaign
“If she fails to back down, Theresa May's approach to Brexit poses a direct threat to our national security."
The Conservative Party have hit back at the claims, accusing the Lib Dems of “peddling nonsense”.
A Tory spokesman said: “We’ve made clear that under Theresa May security cooperation will be an important priority in the negotiations, and it's not in the EU's interest to lessen that relationship."
The Government’s own Brexit white paper, published earlier this year, sets out ministers’ hopes to "negotiate the best deal we can with the EU to cooperate in the fight against crime and terrorism", adding that "public safety in the UK and the rest of Europe will be at the heart of this aspect of our negotiation".
Ukip’s home affairs spokeswoman Jane Collins MEP responded to Mr Clegg’s comments, saying: "The schengen information system is hardly useful to countries who can't stop criminals from entering the country thanks to EU rules and open borders which have made us less safe."
"The priority of Home Affairs is to strengthen the UK internally, making life safer for law abiding citizens and, working with other agencies, to protect the UK from threats from abroad.
"Successive governments, including Theresa May as Home Secretary, have arguably made us less safe with cuts to border forces, EU legislation such as the critical infrastructure directive and open borders with an immigration policy of letting anyone in despite warnings from ISIS they would 'flood' the continent with jihadis.
"We contribute more information to Europol than any other country. We are also a member of Five Eyes.
"It appears Nick Clegg is entirely ignorant of these facts or he is trying to scare and deceive the voters in a rehash of the failed Project Fear from the referendum campaign."