Plans to buy extra trains to tackle overcrowding on the Jubilee and Northern lines have been put on hold.
The Jubilee line was expected to get ten new trains to operate a 36 trains per hour service, while seventeen trains were supposed to be bought for the Northern line as part of the upgrade.
However, Transport for London confirmed the upgrade had been “temporarily paused”.
Train drivers’ union ASLEF has claimed the delay will mean overcrowding will get worse and could result in an “outright cancellation” of the project altogether.
Finn Brennan, ASLEF’s organiser on London Underground, said: “It is deeply disappointing and looks like a classic example of making medium-term savings that damage the long-term ability of the Tube to cope with London’s growth.
“Without new trains, overcrowding will get worse and worse, and the Northern line risks returning to the days when it was known to millions of Londoners as the ‘misery line’.”
Councillor Mark Williams, Southwark’s cabinet member for regeneration, said he would be writing to Mayor of London Sadiq Khan to outline his concerns and urge him to assign funding to the “vital upgrade”.
“This major delay is extremely disappointing for us, and for residents, who share our view that the Jubilee line upgrade is central to our plans for positive improvements to the Canada Water area,” he said.
“We need these additional trains to meet current and future demand and for residents to easily connect with the rest of London.”
David Hughes, London Underground’s director for strategy and network development, said: “The benefits from the largest investment programme in the Tube’s history, combined with the huge capacity increases coming soon from the arrival of the Elizabeth line, means that we are temporarily pausing our plans to buy more trains for the Jubilee and Northern lines.
“Our modernisation programme and in-depth technical work by our new combined engineering division has improved performance and reliability.
“This means we can increase the frequency of our existing trains without the immediate need for new trains, making journeys quicker and more comfortable for thousands of customers every day.”