Government departments in Britain are being asked to produce plans for spending cuts of up to 40%.
The Treasury wants departmental heads to set out how they would cut spending by both 25% and 40% by the end of July.
But education and defence have been given some protection; they have to plan for cuts of 10% and 20%.
Health will continue to have small rises in its budget and international aid is also protected.
The BBC reports ministers were told by the Treasury at a cabinet meeting last Tuesday to draw up what are called "illustrative plans" and have them ready by the end of July.
All departments have also been told to look at cutting their administration costs by a third, or even a half.