Striking Luas workers have been accused of disrespecting commuters and the travelling public after announcing four more planned walkouts.
Trade union Siptu notified the tram network operator Transdev of further 48-hour stoppages on the weekends of April 2-3 and April 23-24 after talks failed to make any progress earlier this week.
Owen Reidy, workers' representative, claimed the company had refused to engage when it came to discussing terms and conditions of employment.
"Despite Luas drivers substantially moderating their pay claim, Transdev is refusing to engage in negotiations. This situation, where an employer is treating workers with such disrespect, leaves them with no option but to escalate their industrial action," he said.
The dispute appears to have split workers as Transdev is to revive talks with the traffic supervisors and the revenue protection officers and supervisors on Friday. Drivers are not included in the next round of talks.
Gerry Madden, Transdev chief executive, expressed disbelief at the deepening strike threat.
"The public, Luas customers and businesses are the real losers here," he said.
"I'm disappointed with the notice served today and the total disrespect being shown to the public."
The additional strike days compound a crisis for public transport in Dublin already threatening St Patrick's Day and Easter Sunday when hundreds of thousands of people will be making their way into the city.
Talks at the Workplace Relations Commission aimed at averting further strikes broke down earlier this week.
The Luas workers had reduced their pay claims but the sides remained so far apart on the drivers' demands that the mediators warned there was no value in sitting at a negotiating table.
Mr Reidy said: "This exclusion of the Luas drivers from the negotiation process must end.
"The company is acting in an unacceptable manner towards this grade of workers. Siptu representatives will be attending talks tomorrow at the Workplace Relations Commission in relation to pay claims by other grades of staff at Luas."
