Union leaders claim they have uncovered proposals to transfer civil service posts overseas, which could result in tens of thousands of jobs being lost.
Unions say tens of thousands of jobs could be lost
The Public and Commercial Services Union says the plan is revealed in an internal leaked document from the Department for Work and Pensions (DWP).
But the government has strongly denied it plans to move jobs offshore.
DWP staff are due to take part in a two-day nationwide strike on 26 and 27 January over plans to cut 30,000 jobs.
These cuts would affect staff in JobCentres, benefit offices, pension centres and the Child Support Agency.
The DWP document Offshoring Process stated: "In line with the continuing need for government departments to reduce costs, proposals are being made by service providers to undertake work for or on behalf of the department overseas.
"This could involve the transfer of part or even all of the functions of a DWP area of business that would have previously been located in the UK, to a centre located outside of the UK."
Mark Serwotka, of the PCS union, said it was "appalling" that the plan had not been discussed with the workers.
"The government now seems to be embracing not only potential privatisation but potentially public sector jobs being shipped overseas."
He said there was a "frenzy" to cut jobs and costs at the DWP, adding that such moves had done nothing to increase the efficiency of the department.
Leigh Lewis, a senior official at the DWP, denied there were any plans to move civil service jobs out of the country.
"We have not moved any of the department's jobs offshore and we have absolutely no intention of doing so.
"Like other very big organisations we have got a huge number of suppliers. Of course it's possible that they may want to outsource some of their work overseas."
He denied that cost-cutting exercises were causing problems, saying services were being delivered "overwhelmingly" efficiently.
The BBC's industrial relations correspondent said the leak would "strain relations" between the union and the department just days before the planned strike action.
Chancellor Gordon Brown has already announced plans to axe 104,000 jobs across the civil service to free up money for education, health, defence, housing and overseas aid.