In September, a woman in her 60s waited for more than two hours for hospital transport after gruelling treatment.

Simone Simmons, from Hendon, finished her treatment at the Macmillan Cancer Centre in London, and was to be collected by private contractor G4S.

Eventually Ms Simmons, a wheelchair user, called a minicab in order to get home in time to see her carer.

The former health worker said: "They cannot leave very sick, vulnerable patients who are in a bad state anywhere - you just do not leave them waiting and waiting without any tea or coffee or even water.

"When I worked at the Royal Free there were times when transport could not always be on time but in those days at least people did not wait like this - not at all."

Russell Hobbs, managing director of transport services at G4S, apologised for the inconvenience, as on the occasion there was an unusually high demand which resulted in an unforseeable delay.

He confirmed they had apologised to Ms Simmons as well.