A second Central line strike will take place next month if transport bosses and unions cannot resolve their conflict.
ASLEF workers will walk out for 24 hours on Wednesday September 17 should a resolution to the dispute with TfL not be found.
A strike last Friday caused chaos for commuters on the Central and Waterloo and City lines, with workers claiming they are being treated unfairly over sick leave and delays on the line.
The union's district organiser Finn Brennan said: "The issues at the heart of this dispute aren’t going to go away.
"London Underground says this is an unnecessary strike, but they don’t seem prepared to deal with the problems we have raised."
Operations director for the Central line, Peter McNaught, said: “We have been in contact with ASLEF during this week and we will be holding meetings at ACAS next week where we urge ASLEF to join us to continue meaningful discussions.
"Further strike action is not necessary and will only serve to disrupt hardworking Londoners.
"I urge the ASLEF leadership to call off their planned industrial action and to work with us to resolve any outstanding concerns."