Birmingham City Council is days away from confirming the biggest spending cuts for decades, with an admission that thousands of local authority jobs will disappear over the next four years.

Council chief executive Stephen Hughes has written personally to the 55,000-strong workforce warning of “difficult and painful” decisions, and he does not rule out the possibility of compulsory redundancies.

His letter follows a two-day brainstorming session by leaders of the council’s Conservative-Liberal Democrat coalition and chief officers to discuss ways of delivering up to £330 million of Government-imposed savings.

Warning staff to start planning their own futures, Mr Hughes states that he is proud of the “professional and caring approach” shown by council workers during a period of great uncertainty about job security.

Details of the proposed cuts package on a department by department basis will be released for public consultation within days, Mr Hughes confirmed.

A special issue of the council newspaper Forward will be sent to every house in Birmingham detailing the impact on services.

Councillors will make a final decision on where the cuts should be made at what is certain to be a stormy full council meeting on March 1.

In his letter, Mr Hughes says the latest estimate of the savings required is “a bit lower” than £330 million, but he does not give a figure.

Any good news is short-lived, since the Government has told Birmingham City Council it must deliver half of the total savings in a single year.

The decision may force the local authority to slash at least £150 million from its budget during 2011-12.

Mr Hughes warned: “The proposals in their entirety will require a significant reduction in the workforce by a combination of natural wastage, early retirement and voluntary redundancy, transfer to other organisation structures and, as a last resort, by compulsory redundancy.”

Addressing staff directly, Mr Hughes added: “Within the next week or so you will have much greater information about how our future budget is likely to affect you.

“I believe it is important that staff are told as soon as possible what the shape of the changes are likely to be, both so that you can contribute to the consultation, and so that you can think about and begin to plan your own futures.

“I cannot pretend that this is anything but difficult and painful.  But I admire your dedication and commitment to Birmingham and I know that despite these changes I will be able to count on a continued professional and caring approach to the delivery of services.

“I am proud of you all and so should all of Birmingham.”

Sources close to Mr Hughes rejected claims by some councillors that the more radical options for cutting, including offloading services to the private and voluntary sectors, had been dropped.

One ally of the chief executive said: “Stephen doesn’t recognise these claims.”