By Peter Wozniak
The Public and Commercial Services Union (PCS) has rejected a government offer on the reform of civil servants' redundancy payments.
There are six unions representing civil servants, all of which legally need to agree to a change before it can go through.
PCS is claimed by the government to be the only one not to have accepted the latest offer.
Currently civil servants taking voluntary redundancy are awarded six years salary - something the government claims is unsustainable giving public spending constraints.
The government's offer was revised up from replacing that with 15 months' salary to 21 months, but PCS remains stubbornly opposed.
Cabinet Office minister Francis Maude had little praise for the union's leadership.
"The previous scheme was simply no longer fit for purpose and had to change," he said.
"In today's tough economic climate, we would be failing in our duty to the taxpaying public if we had allowed its excesses, which saw some employees walking away with packages worth more than six years' pay, to continue.
"There is of course one name missing from the list of unions, the PCS. I greatly appreciate the efforts of the five other unions whose constructive proposals have allowed us to reach these new terms."
Mark Serwotka, the PCS general secretary, piled scorn on any proposed changes.
"We represent the overwhelming bulk of the people whose jobs will be under threat in the uncertain times that we're in," he told the Today programme.
"They are reducing by two thirds the amounts of compulsory redundancy payments. They are removing people accrued rights that they have got over many years of service in an attempt to make it cheaper to sack people.
"Not only is that unfair, it actually flies in the face of two high court rulings that said this approach was unlawful without our agreement when the previous government tried to do something similar."
Mr Serwotka also claimed that another of the civil service unions, the Prison Officers' Association, had not in fact agreed to the new deal and went as far as to claim.
He added: "People are being misled in an attempt into try to bully them into thinking they have to go and they have to go on reduced terms."
The government's claims were further undermined by Unite, who claim that the impression made by Francis Maude that acceptance of the government offer is a "done deal" was mistaken.
Kevin Coyne, a Unite officer said: "Unite has not backed the deal, neither have the other four unions - Prospect, the FDA, Prison Officers Association, and the GMB.
"We are simply recommending this package as the best deal achievable by negotiation. It is up to our members now to decide if they wish to accept or reject this deal.
"It is up to our members to decide the next step and no deal will be imposed on them by leaders of a trade union, especially not Unite."
The previous Labour administration also attempted reform of civil service redundancy terms, but was frustrated, again by the PCS - who managed to get the proposals thrown out of court.