The Department of Public Expenditure and Reform has warned that the protections against pay cuts and compulsory redundancies in the first Croke Park Agreement will cease if the proposals for a successor agreement are voted down by unions.
It has also confirmed that it has commenced preparing legislation to implement the reductions.
The legislation will be required even if the proposals are accepted by unions.
However, four unions opposed to the new proposals have accused the department of "scaremongering".
In a statement, the Alliance of Unions for a No Vote described that claim as "misleading, inaccurate and a gross interference in the democratic decision-making process".
The alliance comprises the INMO, the IMO, the CPSU and Unite.
It accused the department of attempting to unilaterally rewrite the basis on which the talks took place in the first instance.
An alliance spokesperson said it was a clear understanding among unions that if the new proposals were rejected, the original Croke Park deal would remain in place until 2014.
The alliance said the original invitation to talks from DPER Secretary General Robert Watt had never suggested that Croke Park would cease, nor did it ever describe the talks as setting out to end Croke Park and set up a new stand-alone agreement.
It said the draft LRC proposals also indicate that unions are being asked to vote on an extension to Croke Park, not its termination.
The spokesperson said it was most unfortunate that the employer was seeking to threaten workers during a democratic ballot with compulsory redundancies and further pay cuts, especially when the department knew "full well" that Croke Park will stand even if the LRC draft proposal is voted down.
He said the Department may well at that time choose to advise the Government to break Croke Park or to invoke the inability to pay clause contained in it, but otherwise the first deal stands.
The ballot of public sector unions is due to be complete by 17 April.
Earlier, in a statement, the Department of Public Expenditure and Reform said it respected and did not wish to interfere in the democratic trade union process on ratifying the proposals.
However, it rejected the INMO claims that the current Croke Park Agreement would extend to the middle of 2014, or that no pay cuts were required.
The department said that the pay bill reduction of an additional €1bn would be required whether or not the agreement is ratified.
It stated: "If the current recommendation wasn't to be ratified the current agreement would cease, along with the protections it gives, as new measures would be required."
The department says that this was "clearly communicated" to the Public Services Committee before the talks.
The department also disputes an actuarial assessment published by the 24/7 Frontline Alliance yesterday, stating that employees could lose up to 11.4% of their earnings under the new proposals.