A 21-year-old man was wrongly convicted and fined under new Covid-19 laws in what has been described as an “astonishing” misuse of powers.

The Metropolitan Police said the charge has been set aside after the Coronavirus Act 2020 was “incorrectly” used.

The force, which is the largest in the UK, also said the case of a 15-year-old boy is being “re-examined” by the Crown Prosecution Service (CPS).

Both cases were identified by the PA news agency in an analysis of available London magistrates’ court lists.

Warwickshire Police said on Tuesday all outstanding charges brought under the Coronavirus Act, which are yet to go before the court, would be dropped.

They include a charge of failing to comply with a restriction imposed under the Act against Robert Grant, 27, from Nuneaton, who is due before magistrates also charged with drink driving and aggravated vehicle taking, following a collision in Bedworth.

Kirsty Brimelow QC, a barrister at Doughty Street Chambers, told PA: “It is astonishing that the police and lawyers and magistrates are continuing to get the law so wrong.”

The Coronavirus Act, which came into force last month, allows officers to remove or detain a “suspected infectious person” for screening and assessment with “reasonable force” if necessary.

Police were given separate powers to break up gatherings and fine people breaching restriction of movement rules under the Health Protection Regulations 2020.

A 21-year-old man, who PA has chosen not to name as he faces outstanding charges, was arrested outside Tooting Leisure Centre on March 28.

He was later charged with possession of class B drugs, going equipped to steal and acting contrary to paragraph 23(1)(a) and (2) of schedule 21 to the Coronavirus Act.

He pleaded guilty to all offences two days later at Wimbledon Magistrates’ Court and was fined £200 for possession of drugs and £60 for the offence under the Coronavirus Act.

When first contacted about the case, the Met said it was not being reviewed but after further questioning last week, the force admitted: “It was identified this legislation had been applied incorrectly.

“The charge and fine were subsequently set aside. The charges for possession of class B drugs and going equipped to steal were not overturned and the £200 fine stands.

“In this case officers were rightly dealing with an individual suspected of a separate crime and who was also in a public space without a valid reason.

“However, (he) was incorrectly charged with an offence under the Coronavirus Act 2020. This legislation only relates to ‘potentially infectious persons’ which was not applicable in these circumstances.

“This is very new legislation and we have been working with all of our frontline officers to help them interpret and understand it. This includes sharing the recent guidance from the National Police Chiefs’ Council and the College of Policing.

“The officers involved have been spoken to and reminded of the way the legislation should be applied.”

It comes after Marie Dinou, 41, was wrongly fined £660 under the Coronavirus Act after she was arrested at Newcastle Central Station by British Transport Police.

Other forces have been accused of using heavy-handed tactics, with Northamptonshire Police Chief Constable Nick Adderley earning a rebuke from Home Secretary Priti Patel last week over suggestions his officers could start checking shopping trolleys.

Silkie Carlo, director of Big Brother Watch, said: “It’s astonishing that after a string of damaging failures, the emergency legislation is still being misused.

“These sweeping powers to fine and detain people are so broad that police may try to apply them to any one of us.

“We are in truly dangerous territory with such expansive powers, and the police’s inability to use them adequately is severely damaging public trust as well as the rule of law.”

The Met said another case, involving a 15-year-old boy, was being “re-examined” by the CPS after he was arrested in Kingston, south-west London, on April 2.

The teenager denied charges of possession of a bladed article in a public place and failure to comply with a restriction contrary to paragraph 23(1)(a) and (2) of schedule 21 to the Coronavirus Act at Wimbledon Magistrates’ Court the following day and is due back before the same court on May 6.

A CPS spokesman said: “We keep cases under review and that will be considered at the next hearing.”

The spokesman said no figures were yet available on the number of charges brought under the Coronavirus Act or how many were being reviewed.

Raj Chada, head of the criminal defence department and a partner at firm Hodge Jones & Allen, said mistakes could see forces facing legal action.

“There’s clearly two sets of rules that are open to the police and neither the police nor the lawyers themselves seem to be familiar enough with which laws they should be using,” he said.

“That’s just basic training and understanding of the rules.

“Fines will be rescinded and convictions overturned. It certainly will open up forces to civil cases.”