A civil service union is to campaign against the new national partnership programme, claiming it is a "bad deal for lower-paid workers".
The Civil and Public Service Union, which represents more than 13,000 lower-paid civil and public servants, claimed yesterday the proposed new agreement is "fatally flawed".
As final amendments continue to be made to the overall partnership deal, several unions are lining up to oppose the pay elements.
Mr Blair Horan, the CPSU general secretary, said lower-paid workers would lose out in terms of basic pay and trade union rights.
"This deal is bad for these workers because their wages will not stay in line with rising costs," he said. In addition, binding arbitration clauses would enable employers to impose change without agreement, Mr Blair said.
This would "make life much more difficult for trade unions and leave workers in a much weaker position in the future".
Several private-sector unions have already expressed dissatisfaction with the terms of the deal, but the CPSU is the first in the public sector to declare outright opposition.
Unlike colleagues on higher civil grades, CPSU members feel they did not fare well in the benchmarking review.
The union represents clerical and staff officers at the bottom of the civil service pay scale, who were awarded increases of between 8.5 per cent and 10 per cent by the benchmarking body, compared to 13.8 per cent for assistant principal officers.
Mr Horan said it was adding "insult to injury" that full payment of the benchmarking rises had been put off until June 2005.
Under the terms of the deal negotiated between unions and the Government last month, public servants would receive 25 per cent of the benchmarking increases immediately and a further 50 per cent next January.
However, Mr Horan said low- paid public service workers would get no general pay increase this year to help cope with the "ever rising cost of living".
Another public service union, the Irish National Teachers' Organisation, has also expressed "disappointment and anger" at several aspects of the benchmarking proposals, including the time-frame for payments.
At a special delegate conference at the weekend, however, there was "general acceptance" that the deal was the best that could be obtained in the circumstances, the union said in a statement. Its executive meets on Thursday to make arrangements for a ballot.
A Government spokeswoman said "textual changes" to the economic and social programme negotiated by the social partners up to the weekend were continuing to be discussed yesterday.
It is expected the text will be finalised tomorrow. Other outstanding details are expected to be completed by the end of the week.
The proposed agreement will then go back to the social partners for ratification, with the ICTU and the employers' body, IBEC, both planning to have final decisions by mid-March.