"All units should tighten the regulation of cars and cut down the size of the fleet to a controlled scale. The number of automobiles should not be increased unless a new department is formed," said a circular issued earlier this week by the government.
It said excess cars, or those violating pollution standards, should be removed from service by year-end.
The circular asked all officials to "strictly abide by" regulations on car use and be first movers in the use of domestic, low-emission, economic and manual-transmission cars.
"Except for special needs, all units, in principle, should not use off-road vehicles," it said.
The circular said departments could not purchase cars on their own without central government approval.
High-emission, heavy-pollution cars should be replaced before June 2008, the circular ordered.
Government departments were also told to use cars less often and more efficiently, use more public transport outside of Beijing, and avoid using official vehicles during festivals or large national events.
Official vehicles were not to be used in private business or leased for commercial purposes, the circular warned.
It also said that using seniority to gain the use of government cars owned by lower-level departments, or accepting vehicle donations from private enterprises, were both strictly banned.
The circular asked all departments to standardize driving rules to conserve gasoline, with a goal of cutting usage about 20 percent by the end of next year.
Besides energy and environmental concerns, the tightening of government car use is part of a national drive to ease traffic congestion in major cities such as Beijing and Shanghai.
In the country's first nationwide urban public transport week, called "No Car Day", in September, many government officials in a large number of cities chose to take buses to show their determination to develop public transportation and ease worsening traffic jams.