Tram engineers and fitters working for Transport for London are set to strike from 20.00 on 5 May to 06.00 on 9 May, after talks over pay differentials had broken down.

The two sides have clashed over allegations of ‘bad faith’ made by the engineers’ union Unite, which TfL denies.

TfL is advising its passengers to walk, cycle or use buses or the Overground on strike days, when no tram services are expected before 07.00 or after 18.00. During the day reduced frequencies are predicted between Wimbledon and Reeves Corner on the edge of Croydon town centre, and between East Croydon and Beckenham Junction or New Addington.

Unite has warned that more industrial action will follow unless there is an agreement in the meantime.

The argument concerns about 60 tram, stores and infrastructure engineers, who are angry that their staff on the London Underground who require the same qualifications and perform the same duties, are paid up to £10,000 more a year.

Strikes in March were postponed to allow for talks with TfL. Negotiations collapsed, however, with Unite accusing TfL of refusing ‘to be transparent about the process it was using to identify pay disparities and broke its word on how they would be resolved’.

Unite general secretary Sharon Graham said: ‘It is outrageous that TfL somehow thinks it is acceptable to be systemically underpaying highly skilled workers who are essential to keep the tram system functioning.

‘TfL was negotiating in bad faith by breaking its promises and withholding information. Unite’s patience has run out with TfL’s disgraceful double-dealing and lack of transparency.’

According to Unite, TfL has identified five jobs where disparities exist, but has not adjusted the pay of the employees involved.

Unite regional officer Bruce Swann said: ‘TfL is entirely responsible for the disruption that will be caused to passengers. If TfL had stuck to its word and engaged openly and honestly, the Tramlink engineers would not be forced to take strike action. TfL has left these issues to fester for years and the strikes will continue until it resolves them to our members’ satisfaction.’

Another cause of the dispute is that the engineers are on office worker contracts despite their technical responsibilities, which has also affected their pay, and there has been no movement from TfL.

Transport for London responded: ‘We would never enter conversations in bad faith, and have been open and honest throughout the process. We have agreed to work with union colleagues to identify equivalent roles in London Underground, assess any disparity in overall benefits packages, and where agreed take action where appropriate. This will take time and we have asked that this strike action is suspended to allow this to happen.

‘We remain committed to continued dialogue to reach a conclusion and ask the union to suspend this action, which will only cause unnecessary inconvenience for our customers.’

TfL added that where disparities are identified and it is agreed that an increase in pay is appropriate, TfL will commit to resolving that disparity over the shortest time possible, which will be no more than three years. It also said that the introduction of new contracts which TfL had agreed with Unite in December needs ’complex IT changes’, and that it remains committed to making these changes as quickly as it can.