Boris Johnson: Understandable to ask how London Bridge attacker slipped the net

Security services have come under pressure after it was revealed that Khuram Butt, 27, had appeared on Channel 4 documentary The Jihadis Next Door and had also been reported to the anti-terror hotline in 2015.

Mr Johnson acknowledged the concerns as he took aim at criticism from Labour over cuts to policing, saying blaming police resources for the attacks “detracts from the responsibility of these scumbags”

He told BBC Breakfast: “People are understandably right to look at photographs in today’s papers of the TV show that this guy was in and to ask what happened, how did this person slip through our net in the way that he seems to have done?

“I can’t really comment much about that because there is a live ongoing investigation, but one point I would make for all our viewers is it is very important that we look at this issue, when we look at policing, that we don’t take the focus on responsibility away from the people who did it, from the terrorists.”

Labour leader Jeremy Corbyn has called for Prime Minister Theresa May to resign over Government cuts which left the police with 20,000 fewer officers than in 2010.

Mr Johnson told the programme: “When Jeremy Corbyn says it’s all a function of police numbers, I have to say first of all I think that is wrong, police numbers in London have remained high.

“Secondly, we protected police budgets in 2015 and the Labour Party, as I recall, wanted to cut them by 10%.

“All that arguably detracts from the responsibility of these scumbags and what they have done, and we should not allow that to happen.”

Mr Johnson ruled out the need for an independent review into why the attackers were not picked up by intelligence staff, telling BBC Radio 4’s Today programme he was “absolutely certain” that answers would be found.

In a sign of how security is dominating the final days of the election campaign, he repeatedly railed against Labour’s record on security and defence.

He sidestepped questions on how he had opposed 90-day detention of suspects in Parliament, adding: “Of course there are measures that I have not supported myself but the vast majority of measures that have come before the House of Commons I have supported ... but Jeremy Corbyn has opposed every single one.

“Not only that but he has sent out a signal that he is personally opposed to the use of shoot-to-kill tactics which were invaluable in saving people’s lives on Saturday night.”

In a heated interview which culminated in presenter Mishal Hussain telling the Foreign Secretary to “please stop talking”, Mr Johnson was challenged on the claims by Ms Hussain, who read Mr Corbyn’s remarks saying he would give “full authority for the police to use whatever force is necessary”.

He sought to defend the Government’s record, saying the Tories had increased the number of armed officers and plan to boost funding for intelligence services by £500 million.