Drivers at Dublin Bus have rejected Labour Court recommendations aimed at ending a dispute over the company's €11.7m cost saving plan.
Members of SIPTU and the National Bus and Rail Union who were balloted on the deal voted decisively against it.
SIPTU workers rejected the deal by 72% to 28%.
Members of the NBRU voted against it with a margin of 67% to 33%.
The results of ballots of six other grades of workers at Dublin Bus have still to be completed.
In a statement, Dublin Bus said it was extremely disappointed with the outcome of the ballot.
The company said it would now await the outcome of the ballots of the other grades.
Workers went on a three-day strike over cost-cutting at the company two weeks ago.
After that, a proposed deal was struck between unions and management at the Labour Court, which union members have been voting on.
SIPTU Sector Organiser Willie Noone said: "It is quite clear that the drivers in Dublin Bus are not willing to accept the cost cutting measures as outlined in the Labour Court recommendation and subsequent adjustments to it."