In its response to the Cabinet Office consultation, the union said the proposals are the product of political dogma and demonstrate a disdain for loyal public servants.

The government has not produced any evidence to justify the proposed changes. Prospect believes that they are driven by arbitrary targets to reduce severance costs which are not based on fact or evidence.

Prospect also told the Cabinet Office that the proposed arrangements will reduce employers' flexibility to seek and attract volunteers – not increase it.

Garry Graham, deputy general secretary, said: “Many members will question the good faith of the consultation. When the current Civil Service Compensation Scheme arrangements were negotiated in 2010, the then minister for the Cabinet Office, Francis Maude described them as ‘fair for the taxpayer and fit for the long term’.

“Many members will be asking ‘What has changed?’ It is presumably the position of the government that the economy is stronger now than it was in 2010.

“The current approach taken in the civil service already restricts exit payments for longer service and higher-paid individuals. Any further restriction will impact on the ability of the civil service to react flexibly to change and maintain service delivery,” he added.

Prospect is calling for further talks to take place and has made it clear that members will be balloted on any proposed changes to the current arrangements.