Police are afraid of pursuing muggers on mopeds because their careers and lives could be ruined if a chase ends with a criminal being injured and an investigation launched, a police leader has said.

The stark warning from the Police Federation, which represents rank and file officers, comes as it emerged a 24-year-old woman was fighting for her life after robbers on a scooter attacked her stealing her bag and phone.

A moped gang wielding knives and hammers also targeted a jewellery shop, in the capital’s Regent Street, the third time in four months Watches of Switzerland has been raided. One man has been arrested.

Meanwhile, on Monday comedian Michael McIntyre was robbed of his watch after a men on a scooter smashed his car windows while he was on the school run in Hampstead.