Members of the Teachers’ Union of Ireland (TUI) have voted to reject the proposed new public service pay deal.
Members rejected it by a margin of 87% to 13%, on a turnout of 52%.
While a simultaneous ballot also recommended a campaign of industrial action, up to and including strike action due to what they say is pay inequality.
The TUI says its executive committee will decide on what to do with this mandate "in due course."
The union's executive committee had recommended rejection of the proposed agreement.
TUI President Joanne Irwin said: "Throughout the negotiations that led to this proposed agreement, TUI clearly and unambiguously identified the issue of pay equality for those appointed after 1st January 2011 as being of primary importance.
"It is morally wrong that two colleagues are placed on significantly different pay scales although carrying out the same work."
Members of the trade union SIPTU have previously voted to support the new pay deal, as did the Association of Higher Civil and Public Servants (AHCPS).
While the Irish National Teachers' Organisation (INTO) rejected the proposals by a majority of 89% back in July.