Britain's membership of the European Union is putting the security of the country at risk, the Armed Forces minister has warned.
Penny Mordaunt said the UK was unable "share the intelligence we need to keep us safe" as a member of the EU.
Speaking at a pro-Brexit LGBT event in central London on Wednesday evening, the Conservative defence minister also said the "freedom" enjoyed by gay people in the UK was "at stake" at the June referendum.
Defence secretary Michael Fallon, Mordaunt's boss, is campaigning alongside David Cameron for the UK to remain a member of the EU.
He said last night now was "not the time" for the UK to leave the EU and it was "ridiculous" to argue membership put British citizens at risk.
In a video message played at the event, Boris Johnson also encouraged gay people to vote for Brexit.
We can’t form the alliances, we can’t share the intelligence we need to keep us safe.Defence minister Penny Mordaunt
In the wake of the terrorist attack on Brussels on Monday, Mordaunt told the LGBT audience: "I understand that you understand why that freedom is so important. I understand, as well that you know, that freedom needs defending.
"The freedom for every individual, every human being to thrive, to reach their full potential. And to do that we need democracy. We need accountability. And we need our sovereignty back."
Mordaunt said the "gains that have been made" in LGBT rights had been "because of that accountability, because of public pressure and because of our parliament".
"All that is at stake," the minister said. "It’s not just that freedom, but our ability also to defend it, which a subject very close to my heart."
Mordaunt attacked the "forced harmonization" imposed by the EU which she said was "creating such immense austerity" and "meaning that people can't have the prosperity they need to thrive to reach their full ambitions"
The Royal Naval Reservist whose ministerial position puts her in charge of the Armed Forces, was critical of "the constraints that are being placed on our defence and security services so we don’t have the freedom of operation that we need".
"We can’t form the alliances, we can’t share the intelligence we need to keep us safe. All of those things are stifling us and undermining our freedoms," she said.
Mordaunt said people shold vote for Brexit because "we need to defend freedom".
We have a few weeks left to really give our nation the freedom it needs to thrive. Give Europe the impetus it needs to reform. To safeguard those freedoms we hold dear," she said.
Speaking to BBC Newsnight on Wednesday evening, defence secretary Fallon said "this is not the time for us to be leaving an international partnership like the EU".
"The EU has open borders, which were are not part of happily. We have control of our own borders. So we are in a different category from that," he said.
"But we benefit of course. We, in a way, have the advantage of both worlds. We keep control of our borders but we benefit because we share the intelligence, the flight information and the cooperation that there is between security forces across Europe."
Fallon added: "We are not jeopardising the security of our citizens, that is a ridiculous argument."