A request to review the "unduly lenient" sentence of a Croydon man convicted for a "zombie" knife attack was made by Mayor Sadiq Khan, it has emerged.

A public outcry was sparked when Joshua Gardner, 18, was given a suspended sentence for smashing a car window with a large knife, in an incident widely shared on social media.

We reported yesterday that the Attorney General had received a request for the sentence to be reviewed for being unduly lenient.

The Mayor has today revealed that he was behind the referral, releasing the letter he sent to the Attorney General online.

The letter reads: "For those who commit crimes, we need a criminal justice system that provides swift and certain justice.

"To be effective and to main public confidence, jsutice must be done and be seen to be done. Violent offending, in particular, must be seen to have consequences.

"That is why I am requesting that you review the sentence handed down to Joshua Gardner of Croydon.

"I, along with many others, believe this is unduly lenient and does not send the right message tot the public that we are bearing down on violent offenders.

"If Londoners see a situation where somebody branding a zombie knife, like Joshua Gardner, is given a suspended sentence, it risks undermining public confidence in our criminal justice system and fails to act as a deterrent to other intent on committing violent crime."

The Attorney General's office can review sentences given by crown courts if they are considered inappropriate.

Once a member of the public makes a referral, the office has 28 days to review the sentence and make a decision.

The case can then be sent to the court of appeal if the sentence is deemed too lenient. A decision will be made by late December.

The sentence has face criticism from a number of prominent figures in the police force, who argue it undermines their ability to enforce the law.

Met Police Superintendent Roy Smith said : "My personal thoughts are that this sentence does not provide any form of deterrence.

"Nor does it lead frontline officers to feel that they are being fully supported by the rest of the judicial system."

The judge cited a number of mitigating factors when explaining the suspension of sentence, such as that Gardner had already spent six months in custody since his arrest in May and that he had a good chance of rehabilitation.

Gardner, of London Road, was also given a nine month curfew and was ordered to carry out 150 hours of unpaid work.