Britain will be “less safe” if it leaves the EU without a deal with Brussels, a former head of MI5 has warned.
Baroness Manningham-Buller said the country faced a range of security issues – from terrorism to threats from Russia – which were best dealt with in a “European context”.
She said a no-deal Brexit should be avoided “at all costs” and that she was “more than sympathetic” to attempts by backbench MPs to take control of Commons business to prevent it happening.
“I, as a former member of MI5, am very concerned about the loss of things like the European Arrest Warrant, the loss of access to Europol data and so on,” she told BBC Radio 4’s World At One.
“If we leave without a deal we are going to be less safe.
“We have a very serious terrorist problem in this country, very serious other security issues – the rise of Russia, its interference in our elections.
“I am pretty queasy that (Russian President Vladimir) Putin is so in favour of Brexit – I think that should give us all pause.
“There is a range of other security issues – we all face the same one – which are dealt with better in a European context than not.”
Following recent attacks by dissident republicans, Lady Manningham-Buller voiced particular concern about the impact on the security situation on the island of Ireland.
“I am desperately worried. Much of my career was spent working on Provisional IRA, the loyalist terrorist groups in Northern Ireland,” she said.
“I can remember when it was thoroughly unpleasant to go through the border and now, if we go back to that, it cuts off the increasing links between Northern Ireland and the Republic which are an important part of the message of the peace process.
“It will alter dramatically the whole sentiment and politics of Northern Ireland.”
She added: “Throughout the time there has been those who don’t agree with the peace process, who are continuing to mount attacks – generally small-scale.
“But I don’t think it is over in Northern Ireland. The danger is that it gets much worse again.”