Disruption to services on the Northern Line which has led to the closure of Borough station could last until the end of the week.
Borough station was closed on Tuesday and Wednesday whilst the station's staff were redeployed to assist passengers at other stations during the disruption to Northern Line services.
London Underground is advising passengers to avoid the Northern Line and seek an alternative route if at all possible.
The Northern line has suffered from an intermittent train radio fault over the past few days and this has led to a reduced service.
Tube bosses claim that over 80% of services on the line are operating.
The radios have failed in the cabs of Northern Line trains, but drivers can still communicate with line control through the tunnel train radio system. However, for safety reasons, this means that the driver must have another person in the cab in case they collapse or become incapacitated. In these circumstances, the other person in the cab would communicate with line control to advise them and to reassure passengers.
This double staffing means that there are not enough drivers available to operate a full service.