The Rail Maritime and Transport Union said that it was balloting drivers on the Picadilly line in a row over working conditions and agreements.
More top news
Detectives appealing for witnesses to a fatal accident have a released a picture of the 29-year-old victim.
Australian paramedics are being recruited to fill vacancies at the London Ambulance Service.
Brent Council is offering to cut business rates for firms that pay the London Living Wage.