A rail operator has been accused of risking passenger safety if it presses ahead with a plan to remove guards from Overground serives in Waltham Forest.
Transport for London (TfL) recently announced it hopes to remove the guards when it installs new technology on trains on the Barking to Gospel Oak line - leaving the driver as the only member of staff.
But the National Union of Rail, Maritime and Transport Workers (RMT) has vowed to challenge the move, claiming passenger safety will be compromised.
The union said members were prepared to strike over the issue, which affects services running stopping at Leyton MIdland, Leytonstone High Road Blackhorse Road and Walthamstow Queens Road stations.
John Leach, RMT regional organiser for London transport, said: "RMT are going to resist this because we are determined to keep the railway safe.
"Fundamentally we believe all trains should be guarded by a human being.
"Opening and closing doors is part of what they do but not the main part – you can’t run a railway safely without people.
"People are being replaced by technology."
Mr Leach said London Overground Rail Operations Ltd (LOROL), the body that operates Overground services on behalf of TfL, contacted the union out of the blue this month saying they intended to get rid of the guards.
TfL are set to activate a clause in their contract which would see driver only operation on all trains.
Though no final decision has been officially made, a TfL spokesman said LOROL is consulting on TfL’s behalf.
Jonathan Fox, Acting Director of TfL London Rail, said: "We do not believe that the new system will have any impact on safety.
"On the East London Line, which uses driver only operation, the rate of door incidents is one for every 7 million passengers.
"This compares to the section of the network which currently uses conductors, where the rate of door incidents is one for every 4 million passengers."
Mr Fox added that the proposed system would save £5m each year and that all Overground stations will continue to be staffed while trains are running.
Cameras, communication equipment between drivers and the operations base will be installed before guards are scrapped.
Driver only trains currently operate on 60 per cent of the Overground network.
TfL say they do not have a timeframe on the project, but RMT claim the plans are scheduled for completion in 12 months.