A Metropolitan Police officer who used his car to knock a teenager off his moped in a "tactical contact" has been put under criminal investigation.

The unnamed officer struck the scooter to deliberately stop the 17-year-old youth riding dangerously in Erith, southeast London, in November last year.

The teenager, who was not wearing a helmet at the time, was taken to hospital with serious head injuries and fractures but was later discharged.

He later pleaded guilty to five offences at a youth court, including theft, dangerous driving, and driving without a licence.

It comes as political opinion is divided over the use of the controversial stopping technique, which has been defended by the force.

Scotland Yard said the recently-introduced tactic has helped stop dangerous chases and reduced moped crime in London by more than a third.

The manoeuvre has also been backed by Prime Minister Theresa May.

Police watchdog the Independent Office for Police Conduct (IOPC), which is investigating the incident, is due to make a decision soon on whether to submit a file of evidence to the Crown Prosecution Service (CPS) and to Scotland Yard.

If the IOPC recommends a prosecution, it would then be up to CPS bosses to decide whether or not to press charges against the officer, which could include actual bodily harm and grievous bodily harm.

The Met would also make a decision on whether the matter amounted to a misconduct allegation, which could result in the officer leaving the force.

The IOPC is also investigating a second tactical contact case involving another Metropolitan Police officer, which featured an adult moped rider in Ealing, west London, in March.

The second case is not a criminal investigation, but comes as politicians are split over the tactic’s use.

Mrs May said a robust response was needed from police to what she described as a growing problem of people using mopeds to commit crimes such as bag and phone-snatching.

But Labour has raised concerns about the approach, which shadow home secretary Diane Abbott said was potentially very dangerous.

(c) Sky News 2018: Met Police officer under criminal investigation for knocking down moped teen