Updated 10.35 pm

THE NATIONAL BUS and Rail Union has hit out at the use of “scab labour” in the dispute between Luas drivers and operator Transdev.

Transdev, the company which operates the Luas, has said a special bus service will operate on St Patrick’s Day as strike action means there will be no tram services.

The buses will operate from park and ride stops directly to and from the city centre, from 7.30am to 7pm, with a bus every ten minutes.

But this evening the NBRU, which isn’t involved in the dispute, has written to Transport Minister Paschal Donohoe complaining about the use of “scab labour to break a legitimate dispute”.

“It is bizarre that a French company, with that country’s much vaunted social values would resort to a Thatcherite remedy to break this strike,” the NBRU’s general secretary Dermot O’Leary said this evening.

NBRU writes to Minister & condemns Transdev's proposed use of scab labour in LUAS disputehttps://t.co/YSThElkPeG pic.twitter.com/c7VIL5zEHA — NBRU (@NBRU_DUBLIN) March 11, 2016 Source: NBRU /Twitter

Yesterday, Siptu announced four additional strike days, on 2, 3, 23 and 24 April. They had already been scheduled to strike on St Patrick’s Day, Easter Sunday and Easter Monday.

The two sides of the dispute are back in the Workplace Relations Commission (WRC) today, but only to discuss conditions for other grades within the company – not the drivers, who account for 170 of the 250 Luas workers.

Siptu’s Owen Reidy said the company “won’t talk to the drivers so the drivers have no option but to keep announcing actions”.

A spokesperson for Transdev said that Luas pre-paid tickets and Leap cards will be accepted on the buses.

Talks between both sides at the Workplace Relations Commission will resume on Monday.

- Additional reporting by Rónán Duffy