Professor Anthony Glees lambasted the Metropolitan Police for its “lack of planning” after 52-year-old Khalid Masood mowed down members of the public and attempted to storm the Houses of Parliament on Wednesday.
The University of Buckingham academic suggested the incident could have easily been worse if the attacker had been carrying explosives.
He told the BBC’s Victoria Derbyshire programme: “This was a failure of security policy – people may have seen the pictures… of Mrs [Theresa] May being taken at great speed but at an extreme condition of chaos out of Parliament.
“This was somebody [Masood] who got within 100 metres of where the Prime Minister was, if he’d had an explosive vest, you and I would be having a very different conversation now.”
Professor Anthony Glees lambasted the police over PC Keith Palmer's death
A very brave police officer was sent to confront a crazed islamist attacker without a weapon
Professor Anthony Glees
He then bashed acting deputy commissioner Mark Rowley over his reaction to the terror attack, in which three pedestrians were killed.
Professor Glees said: “And when Mr Rowley said ‘oh well, you know, we’ve been planning this for a long time, it [the response] was very proportionate’ – no it wasn’t proportionate at all!
“A very brave police officer was sent to confront a crazed Islamist attacker without a weapon.
“This isn’t planning, it’s lack of planning and I think we’ve become complacent in this country. Nobody wants to see armed police but that is the only response, particularly in Westminster.”
London mourns terror attack at vigil Fri, March 24, 2017
The world grieves after an attacker killed three people and injured about 40 near parliament in London.
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Floral tributes are left after the vigil in Trafalgar Square, London to remember those who lost their lives in the Westminster terrorist attack
Tributes left to PC Keith Palmer following the London terror attack
The criticism comes after Mr Rowley hit out at “armchair critics” knocking acting commissioner Craig Mackey for “leaving the scene” and not staying to help PC Palmer.
He dismissed the criticism as “nonsense” while making a statement on Friday.
Mr Rowley said: “It’s frustrating when we’re wrestling with an issue like this and the acting commissioner’s doing an excellent job that we get nonsense from armchair critics.
“Can we focus please on the investigation and the public appeal.”
Police have since arrested 10 people in connection with the incident.