Commuters relying on the Piccadilly Line could face three days of travel chaos as Tube drivers are set to stage a 52-hour walkout.
Strike action has been planned on the line, which transports around 700,000 people every day, from 9pm on Wednesday July 11 to 1am on Saturday July 14.
The action has been taken by RMT union, one of the biggest unions representing London Underground workers.
This latest strike, which compounds on customers' experiences of delays and gaps in service on the line, is over a dispute between Tube drivers and London Underground .
RMT has said the issue is regarding "a series of attacks on working conditions and staffing levels", which it says has turned the line into a "pressure cooker".
RMT alleges that London Underground has shown a "continued failure" to employ enough drivers to work on the line and the continued breaking of agreements between unions and the Tube operator.
RMT General Secretary Mick Cash said: “There have been repeated problems on the Piccadilly Line going back a number of years which have led to dispute after dispute and the failure of LU management to get a grip has tipped the situation over the edge yet again.
"That is why we have had no option but to put on these strike dates.
"Every effort by RMT reps to negotiate a settlement has been obstructed by the company and it is now down to LU bosses to start listening to their members, take the raft of issues at the heart of this dispute seriously and start engaging in a way that will allow us to make some genuine progress."
However TfL has urged the union to reconsider its action which will heavily disrupt the Tube network spread over four days.
Nigel Holness, Director of Network Operations for London Underground said: "We urge the RMT leadership to work with us constructively on the local issues they have raised rather than threaten to disrupt our customers.
"We remain available for talks to prevent any unnecessary industrial action on the Piccadilly line.”
RMT also cited the ageing Piccadilly line stock, among the oldest on the entire London Underground network as one of the reasons behind the strike action. Some of the trains in operation date back to 1975, but they only had a design life of 40 years, which they have already exceded.
With a significant proportion of the Piccadilly line being above-ground, falling leaves in Autumn have caused issued over the last three years, with 40 trains having to be taken out of service in 2016 alone after they developed "flats".
As a result, while the train's wheels were being replaced and tracks were being improved, commuters on the line experienced heavy delays and long gaps between services, including during rush hour, which had a knock on effect on how busy trains and platforms were.
In June, London Underground announced that it was to sign a contract with Siemens Mobility to get 94 new state-of-the-art "Deep-Tube" trains for the line, with deliveries beginning in 2023.