Pc Paul Fisher, 46, lost control of his unmarked BMW X5 while responding to the stabbing spree carried out by Sudesh Amman in Streatham in south London in February 2020.

The 20-year-old grabbed a large kitchen knife from a hardware store on Streatham High Road, in south London, and stabbed two members of the public before being shot dead by police.

PC Fisher, who was travelling with other armed officers, hit the back of a taxi driver's Toyota before hitting a Ford Fiesta and a garden wall.

The former Royal Marine, who reached speeds of more than 80mph, said he had made a "split-second error".

He was acquitted of dangerous driving following a week-long trial at Southwark Crown Court.

Sir Mark Rowley said: "If an officer makes honest mistakes under the most immense pressure while rushing to a live terrorist incident it cannot be right this is dealt with by a criminal trial nearly four years later.

"That's why the treatment of this brave officer by the systems of accountability is appalling.

"No other country in the world would haul one of its most highly trained officers before a court for responding to one of the most serious incidents we can deal with and doing their utmost to preserve life."

Sir Mark said also his prosecution "further undermines the confidence of all officers using their powers to keep the public safe".

It comes after the Home Office launched a review into firearms policing after many put down their weapons when a marksman, known as NX121, was charged with the murder of Chris Kaba, shot dead in south London last year.

Sir Mark said "the system has to change" or officers will become "more scared" of it "than they are of facing terrorists and criminals intent on attacking communities".

Read more from Sky News:
Oscar Pistorius to be released
13 Israeli hostages on their way to Egypt, local media say

"Officers fully expect to be held accountable for their actions, but they need to know the system holding them to account will be swift, fair, competent, and recognise the split-second decisions made every single day," he added.

"The current set-up clearly fails those tests."

The Independent Office for Police Conduct (IOPC) said the officer's speed along with other evidence led to the police watchdog passing a file to the Crown Prosecution Service (CPS), who authorised the charge.

IOPC regional director Mel Palmer said: "There is no doubt that PC Fisher was responding to a life-threatening incident in February 2020. A jury, having considered all of the evidence, has acquitted him of dangerous driving and we respect that decision."

A CPS spokesperson added: "The CPS does not decide whether a person is guilty of a criminal offence - we make fair, independent and objective assessments about whether it is appropriate to present charges for the court to consider.

"In this case, we decided it was appropriate for a court to consider one charge of dangerous driving. The jury found the defendant not guilty and we respect its verdict."