A 48-hour strike on London’s Docklands Light Railway will go ahead from 4am on Wednesday after talks failed to avert the action.

Transport for London has warned it is unlikely that any DLR services will run during the walkout by members of the Rail, Maritime and Transport union.

A second phase of action will coincide with the London Marathon next month.

Two days of talks at the conciliation service Acas between the union and KeolisAmey Docklands Ltd, which operates the DLR, failed to resolve a dispute over claims of a “comprehensive breakdown” in industrial relations.

RMT general secretary Mick Cash said: “RMT recognises the impact that our action will have and the responsibility for that will be entirely down to the company.

“This dispute is over the fundamental issues of workplace justice, fairness, the outsourcing of key functions and sticking to agreements and practices that Keolis seem to believe that they can trample all over.

“RMT members employed by KAD have had enough of being treated like dirt and have made it clear that they are prepared to stand up and fight for their fundamental rights.”

TfL confirmed it was unlikely any DLR services would run during the 48-hour walkout, and warned that trains might also be affected on the morning of Good Friday.

Extra buses will be laid on and “travel ambassadors” will be on hand to help passengers with information, amid warnings that local Underground lines and stations are expected to be busier than usual.

Mark Davis, TfL’s interim general manager of the DLR, said: “KeolisAmey Docklands predict that it is unlikely that any DLR services will run on Wednesday and Thursday due to strike action by the RMT union.

“Our bus, Tube and rail services will be operating as normal, and we will be running extra buses on key routes to help keep London moving.

“Our services, particularly in east London, are expected to be very busy and we thank everyone for their patience while the strike action takes place. Customers are advised to use our website to plan ahead.”

Abdellah Chajai, managing director of KeolisAmey Docklands, said: “I would like to apologise to passengers for any disruption to their journeys, caused by the RMT union’s strike.

“Following a number of meetings between the management team and RMT, as well as days of discussions under the auspices of Acas, it is very disappointing to find the RMT union refusing to work with us to avert the strike action they have planned.

“Despite our best efforts to resolve the issues the union had raised, they have instead chosen to proceed with the strike and cause unnecessary disruption for our passengers. We advise passengers to seek alternative routes and to check the TfL website before they travel.”