David Cameron’s former policy guru has demanded Theresa May resign for “security failures” that led to terror attacks in Westminster, Manchester and London Bridge.

Steve Hilton said Ms May bore responsibility for the attacks, should not be seeking re-election and had been “blame shifting” in statements since they unfolded.

The accusation will come as a blow to the Prime Minister as she prepares to give a speech on Monday likely to be dominated by efforts to stamp out the terror threat.

Ms May, responsible for the security services since 2010 as Home Secretary and then Prime Minister, has already been attacked by political rivals and police figures over severe cuts.

Mr Hilton, who left Downing Street in 2012, posted reports relating to an alleged suspect of Saturday’s attack, before adding: “Theresa May responsible for security failures of London Bridge, Manchester, Westminster Bridge.

“Should be resigning not seeking re-election.”

Commenting on newspaper reports that appeared to attribute some responsibility to the security services, he went on: “Theresa May blame shifting again.

London Bridge Terror Attack Show all 16 1 /16 London Bridge Terror Attack London Bridge Terror Attack Armed police on Borough High Street as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Armed Police talk to members of the public outside London Bridge Hospital as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Police Officers outside the Barrowboy and Banker Public House on Borough High Street as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Armed Police talk to members of the public outside London Bridge Hospital as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Armed police on Borough High Street as police deal with a 'major incident' at London Bridge PA London Bridge Terror Attack Emergency services near the scene of the incident Screengrab London Bridge Terror Attack People run down Borough High Street as police are dealing with a "major incident" at London Bridge Reuters London Bridge Terror Attack Emergency services arrive at the scene near Borough market at London Bridge Carl Court/Getty Images London Bridge Terror Attack Emergency personnel on London Bridge as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack Police sniffer dogs on London Bridge as police are dealing with a "major incident" at London Bridge PA London Bridge Terror Attack A second helicopter lands on London Bridge as police are responding to three incidents in the capital, amid reports that a vehicle collided with pedestrians on London Bridge, Scotland Yard said. Officers are dealing with reports of stabbings in Borough Market, where armed officers attended and shots were fired. They are also at an incident in the Vauxhall area PA London Bridge Terror Attack Police attend to an incident on London Bridge in London REUTERS London Bridge Terror Attack Police attend to an incident on London Bridge in London, Britain Reuters London Bridge Terror Attack A police officer escorts members of the public to safety at London Bridge Getty Images London Bridge Terror Attack Police attend to an incident on London Bridge in London, Britain Reuters London Bridge Terror Attack Police attend to an incident near London Bridge in London, Britain Reuters

“Her spin doctors attack MI5, but she was in charge of them for years.”

There was a 20 per cent drop in the number of armed officers between 2010 and 2016, when Ms May was at the the Home Office, accompanied by a total reduction of some 20,000 police officers in general.

Speaking on Monday, cabinet minister Karen Bradley said: “It’s not just about numbers, it’s about powers. It’s about making sure the police have the powers they need.”

In her post attack statement Ms May signalled tougher action on terror to come, using the phrase “enough is enough”, before calling for the internet to be more strictly regulated and revealing that counter terrorism strategy would be reviewed to “keep up” with a changing threat.

Jeremy Corbyn tells Theresa May 'you cannot protect the public on the cheap’

But Labour leader Jeremy Corbyn tore into her record, accusing her of trying to “protect the public on the cheap”.