Tooting MP Sadiq Khan has said he fears not enough is being done for residents during the Northern Line closures.
From March 27, the Northern Line will close earlier on weekday evenings and there will be some weekend closures.
In a letter to Richard Parry, managing director of London Underground, Mr Khan said he had serious concerns about alternative transport to serve the area.
“Previous closures on the Northern Line between High Barnett and Edgware received rail replacement bus services.
"I think it is unacceptable that London Underground are not sure if they will provide a replacement bus service during these closures,” wrote Mr Khan.
He also wrote to Chris Burchell, Managing Director of Southern Railway, and Andy Pitt, Managing Director of South West Trains, asking for assurances that train services would be running efficiently during the closure period.
A Transport For London spokesperson said: “We continue to press Tube Lines and its shareholders, Ferrovial and Bechtel to think again and urgently review it's Northern Line programme and work to minimise disruption and delay to Londoners”.
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