It's enough to make British and European car company workers on four or five weeks holiday a year weep: salaried workers at General Motors, who get as little as two weeks holiday a year (that's a normal allocation in the US) can buy up to five extra vacation days this year for $US175 a day, a plan the automaker reportedly says is designed to save millions of dollars and boost morale.

An Associated Press report citing the Detroit News said GM also let white-collar employees buy extra vacation last year. Part-time employees may purchase up to three days. The company would save $34.4 million if every eligible worker took full advantage.

"It's a cost savings for us," GM spokesman Kerry Christopher reportedly told The Detroit News. "But offering more vacation days is something employees really appreciate."

The report said that, last year, 27,500 employees, or 68% of GM's 40,529 salaried US workers, bought an additional five days of vacation and were charged their daily pay rate, which in many cases was more than $175.

GM has reduced its US salaried work force to 39,362 this year, mainly through attrition, the report noted.

The automaker detailed the offer in an e-mail to employees last week. Workers have until Friday to accept.

The offer reportedly is especially popular with employees who have worked for GM less than five years and who receive just those two vacation weeks a year.

Ford employees get "flex dollars" used to buy health and dental insurance. Any remaining flex dollars can be used to buy up to 10 extra vacation days, spokeswoman Marcey Evans told Associated Press.

DaimlerChrysler has a similar programme using a combination of credits and cash. About a third of the company's 15,210 non-union salaried workers have purchased between one and five days, spokeswoman Angela Ford reportedly said.