Members of the Unite trade union have rejected the Haddington Road proposals on public sector pay and conditions.
Almost three quarters of members voted against the deal, which has been proposed as a replacement for the previously rejected Croke Park II document.
Unite represents around 6,000 of the Government's 290,000 employees and joins the CPSU and 2 of the main teachers unions, the TUI and the ASTI, in opposing the deal.
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The union's representatives - who recommended a no vote to members - will meet later this morning to discuss their next step.