A row over toilet breaks is threatening to disrupt journeys for thousands of Tube commuters after a rail union announced a 24-hour strike.

Drivers on the Hammersmith & City Line are due to stop work at 9.30pm on Tuesday December 6th. The action will coincide with a separate strike by RMT members on the Piccadilly Line.

London Underground accused some drivers of spending more than an hour in the toilet. One member of staff is said to have taken a toilet break lasting 127 minutes.

The RMT described the claims as nonsense and insisted its members were the victims of harassment.

People were getting letters about how long they were in the toilet and things like that. Nobdoy's been in the toilet for more than two hours. These drivers at both these depots on this line are fed up to the back teeth of being taken for granted and taken advantage of. JOHN LEACH, RMT

The Piccadilly Line dispute follows a 'breakdown in industrial relations, according to union bosses - although fresh talks at conciliation service ACAS are due tomorrow..> The strikes, on the same day as the next round of industrial action by Southern Railway guards, means train and Tube services to both Gatwick and Heathrow airports face disruption.