Mr Serwotka believes there will be support for the proposed walkout

In a speech to the TUC conference in Brighton he urged unions to back his members in their forthcoming fight.

PCS is to ballot nearly 300,000 members for a one-day strike on 5 November.

Mr Serwotka said: "We urge the government to think again and think through the impact of decimating a fifth of the civil service."

Cut to the bone?

He argues the proposed cuts would result in poorer public services for everyone.

Mr Serwotka contrasted the impact on public service with recent difficulties experienced by air passengers.

"Look at the experience of British Airways this summer - they embarked on a so-called efficiency drive and cut jobs to the bone," he said.

"It's one thing to have your flight to New York cancelled ... but it is another if is your benefit, your pension or your tax credit."

He added: "None of these services should be cut and our members have a right to job security."

Ballot

On Sunday the union confirmed all its members in England, Scotland, Wales and Northern Ireland will be balloted during the first three weeks of October.

Last week Mr Serwotka hinted at possible strike action in an interview with BBC News Online.

Most government departments are likely to be affected by the dispute, including the Home Office, health and transport departments, inland revenue, customs and the Department for Work and Pensions.

Mr Serwotka stressed the PCS was in favour of improving efficiency, but argued job cuts would not be effective.

He accused the government of acting "disgracefully" over the job losses first announced by the Chancellor Gordon Brown in his last Budget.

"The people the government is seeking to axe are not bowler-hatted Sir Humphries or faceless bureaucrats, they provide vital services that touch everyone's lives from cradle to grave."

The union leader said a strike by the civil servants was required in order for the government and members of the public to realise the importance of their work.

Working hours

He also levelled criticism at the Tory party, who have suggested the civil service would be slimmed down under a Conservative government.

"The majority of these politicians are completely out of touch - they should stop this macho political posturing about who can cut the most.

"Offices will close and services deteriorate if these cuts happen", he said.

The planned cuts would cause one in five PCS members to face an uncertain future, while increasing stress levels for those keeping their jobs.

The strike is being planned over a series of issues, mainly the job cuts but also over proposals for longer working hours and threats to civil servant pensions.