Europe’s open borders are putting Britain at risk of terror attacks by letting jihadists pass through the continent unchecked, a former police chief has warned.

On Friday, Italian officials confirmed they had shot and killed Anis Amri, the terrorist behind the Berlin Christmas market attack, after he had travelled through three countries unhindered.

He was only stopped after a chance encounter in Milan with a police officer who happened to recognise him.

Now, a former counter-terror chief has warned that Europe’s open-borders Schengen agreement is putting the continent’s – and Britain’s – security at risk.

Speaking to The Telegraph, Richard Walton, a former head of counter-terrorism at the Metropolitan Police, said: “Schengen poses a huge risk of terrorism, porous borders across mainland Europe are continuing to be exploited by Isil.

“They have a clear strategy and have set out to carry out attacks across mainland Europe. Europe’s weakness is our weakness, it is a concern for us because if you’re neighbours are insecure by definition.

“We need European countries to get their act together. Sooner or later they are going to get across the Channel.”

His comments were echoed by Conservative MP Iain Duncan Smith, who said Britain must leave the European Union as soon as possible if it to get back control of its borders.

“The sooner we get out the stronger our ability to look after ourselves and our borders will be,” he said.

“Where the European Union has been heading is towards this creation of a super state, within which there would be no borders, no controls, no checks. We are now beginning to see what a mistake that has been.”

Earlier this month, Europol, the EU’s law enforcement agency, said it was “indisputable” that terrorists have entered Europe by posing as refugees.

A report by the group added: “France remains high on the target list for IS aggression in the EU, but so too do Belgium, Germany, the Netherlands and the UK.

“Estimates from some intelligence services indicate several dozen people directed by IS may be currently present in Europe with a capability to commit terrorist attacks, and that there are indications that IS has been preparing terrorist attacks in Europe since 2013.”