Public sector unions have until 3pm today to accept the government’s latest pension deal or the “generous” offer could be withdrawn, unions have been told.

The pensions row intensified over the weekend as the Public and Commercial Services Union (PCS) accused the government of “bullying its members” into accepting changes by 10am today or risk exclusion from further talks.

This deadline, described as “arbitrary and unnecessary” by the PCS, has since been pushed back to 3pm today, union sources said. But union leaders remain unhappy with being put under pressure. “We are not in a position to accept what they are asking,” a PCS spokesman complained.

Government ministers want to reduce the cost of employee pensions and have vowed to increase staff contributions and shift pensions from final salary to career average schemes.

But the PCS said that the recent government consultation had revealed a “general rejection of the need to raise contributions.”

Further sticking points for the unions include the rise in the state pension age and the decision to peg annual increases to a lower measure of inflation (Consumer Price Index).

In November, the government made some concessions on the deal, including a more generous accrual rate to build pension pots more quickly, plus protection for workers due to retire in the 10 years from 1 April 2012.

But this failed to break the standoff and UK-wide strike action went ahead on the 30th of November.

PCS general secretary Mark Serwotka said: "We remain committed to the negotiations and will continue to attend all meetings, but ministers only appear to be interested in imposing an unfair and entirely unnecessary tax on people working in the public sector.

"Every single penny raised from contributions would go to the Treasury to pay off the deficit. We remain fundamentally opposed to public servants being forced to pay more and work longer for less in retirement."

The parliamentary recess starts tomorrow, leading to the pressure to agree a deal in the next 24 hours. However, the government refused to confirm or deny that it would end negotiations with union representatives if they did not accept its offer.

In a statement the cabinet office said: “We have been clear that the deadline to reach agreement is by the end of the year and remain hopeful of reaching an agreement by then.”

But speaking to PM last month, Anne Gibson, president of the Public Sector People Managers Association, predicted that pensions talks were likely to continue into 2012.