The Public and Commercial Services (PCS) union has raised the prospect of taking legal action against the government over its planned cuts to civil service redundancy pay.
The Cabinet Office last month unveiled a series of changes to the Civil Service Compensation Scheme arguing that the package, which governs redundancy terms for officials, had become unaffordable.
The planned cuts to redundancy pay would mark the second set of changes to the scheme in just six years.
Civil Service Compensation Scheme: two unions urge members to back redundancy deal
Civil Service Compensation Scheme overhaul — full details & reaction as Cabinet Office makes offer
John Manzoni: redundancy offer is a "fairer deal for civil servants"
Civil Service Compensation Scheme: will you be affected by the redundancy shake-up?
Both the FDA and Prospect unions, which took part in talks with the Cabinet Office over plans to change the scheme, have urged their members to accept what the government has called its "final offer" or run the risk of ministers imposing more stringent cuts to the scheme.
But PCS, the largest of the civil service unions, did not take part in negotiations with the government over the summer, refusing to accept the Cabinet Office's preconditions for talks. Unite and the Prison Officers Association also chose not to participate.
"The union was effectively barred from negotiations with the Cabinet Office because it refused to agree these further cuts were necessary" – PCS
After a special meeting of its executive committee this week, PCS said it was "actively considering mounting a legal challenge to the planned changes", potentially focusing "on the process the government has followed".
"Proposals to again cut the terms on offer under scheme were first announced in February," PCS said in a statement.
"The union was then effectively barred from negotiations with the Cabinet Office because it refused to agree these further cuts were necessary."
PCS said it would ballot its members during November and would recommend that they reject the Cabinet Office's final offer.
"This is not a national industrial action ballot, but the union will keep that option under review," it added.
The prospect of a legal challenge by PCS has echoes of the protracted 2010 court battle in which the union successfully blocked the then-Labour government's cuts to the Compensation Scheme.
However, that action drew fire from other civil service unions, who argue that it prompted the Conservative-led coalition that followed Labour to make its own substantial changes to civil service redundancy pay through an amendment to the Superannuation Bill.
Launching PCS's response to the latest redundancy plans, general secretary Mark Serwotka accused the current government of "seeking to axe tens of thousands more jobs on the cheap".
"With previous cuts to these terms in recent memory, it is reprehensible that staff are being treated with such contempt, and ministers and senior officials have acted in a disgracefully underhand way by preventing any genuine negotiations," he added.
“We are determined to fight the obvious consequences of these cuts with campaigns for jobs and public services in our communities across the UK, and through parliament and the courts if necessary.”