In her letter to the President of the European Council, Donald Tusk, May said: "the United Kingdom wants to agree with the European Union a deep and special partnership that takes in both economic and security cooperation".
However, she hinted that talks on a new trade deal with the EU could be affected by any failure to cooperate on security issues — with Britain playing a prominent role in the EU law enforcement agency Europol — effectively making security a bargaining chip in the Brexit talks.
"In security terms a failure to reach agreement would mean our cooperation in the fight against crime and terrorism would be weakened. In this kind of scenario, both the United Kingdom and the European Union would of course cope with the change, but it is not the outcome that either side should seek," she wrote in her letter to Tusk.
This brought an immediate response form Verhofstadt, who told a press conference it was tantamount to "blackmail."
"I tried to be a gentleman towards a lady, so I didn't even use or think about the use of the word blackmail. I think the security of our citizens is far too important to start a trade-off of one and the other. Both are absolutely necessary in the future partnership without bargaining this one against the other," he said.
Verhofstadt alluded to the issue again in a Facebook broadcast, March 30, in which Sputnik's reporter Jim Ensom posed the question: "Do you think Britain is blackmailing the EU on the issue of security and intelligence?"
"There is one key issue that is very difficult for us to accept. There is a certain chapter in the letter which says 'we [the UK] wants to cooperate on security and the fight against terrorism, but then we need a good deal on trade'. Sorry, that's not the way it's going to work," Verhofstadt said.
"I think that the security of our citizens and the fight against terrorism is so important that you cannot make it a trade-off between security and the economy. It's not serious. The security of the citizens is so important that it needs to be a separate pillar of a future agreement. It's not a trade-off."
Britain's security and defense capabilities — which are seen as a leading strength within the EU — will form a central plank of talks over Brexit and could prove crucial to any new deal. The director of Europol is British-born Rob Wainwright, a former Director, International, of the UK National Criminal Intelligence and Chief of the International Department of the UK Serious Organized Crime Agency.