Commuters in London faced more disruption on Thursday as the Underground, the United Kingdom capital's subway, was again suspended amid a fifth straight day of walkouts that have crippled services and brought travel chaos to the city.

The union representing Underground workers pressed again for a meeting with the city's transit authority, Transport for London, or TfL, to resolve their pay-and-hours dispute and warned further strikes could follow if talks failed to advance.

The Rail, Maritime and Transport union's General Secretary Eddie Dempsey, whose organization represents Underground drivers, signalers, and maintenance workers, repeated his call for London Mayor Sadiq Khan, who chairs TfL, to meet the RMT in a bid to resolve the standoff, reported the London Standard news website.

Negotiations remain deadlocked, with no face-to-face talks being held since last week.

"Instead of going on social media, instead of the old tired cliches, telling trades unionists to get round the table, you're the mayor of London, you're the chair of Transport for London," Dempsey said. "Stop going on social media, invite us to the meeting, let's have a discussion, because I want to know what is going on in London."

Dempsey said there had been "a total collapse of industrial relations" and warned more strike action would follow if no resolution was reached.

He added the union "takes no pleasure in causing disruption" but "makes no apology for fighting for our members".

On Wednesday, TfL negotiations lead Nick Dent said the RMT had made clear talks could not progress without an upfront commitment to cut working hours.

According to the mayor's office, Khan had "ensured TfL is ready to restart talks" with the union to resolve the dispute.

The union had rejected a 3.4 percent pay offer and pushed to reduce members' 35-hour week, which TfL said was unaffordable.

The Docklands Light Railway, or DLR, an automated light metro in the east of London, was also suspended for a second time this week on Thursday as part of separate RMT action.

E-bike use surged in the capital as commuters looked for alternative ways to get around, reported the BBC. Lime, an e-bike operator in the city, reported rush-hour trips were up about 75 percent by Wednesday.

Khan on Thursday called the strikes "ultimately a sign of failure" and urged the RMT and TfL to get back to the negotiating table.

Striking workers are taking action because they cannot afford to buy a home in London on salaries of about 72,000 pounds ($97,270), Dempsey said, as he sought to defend the action that has brought much of the capital to a halt. The union is reported to be seeking a four-day, 32-hour week.

Asked on Times Radio if 72,000 pounds was a good wage, he said "well, you can't afford to buy a house in London, even on 72,000 pounds", arguing workers should be able to live in the city and that buying often requires pay of more than 100,000 pounds.

He later called 72,000 pounds "a good wage", but said better pay and conditions were still justified. Average pay is 65,994 pounds in London and 46,006 pounds in the southeast of England.