Thousands of new permanent 16- to 32-hour-per-week, part-time federal jobs would be created under a Senate bill approved yesterday and sent to President Carter.

The legislation would benefit housewives, students, retirees and others who want to work for Uncle Sam but who cannot put in a full eight-hour day. Currently the government has only 51,000 permanent part-time jobs out of a work force of 2.8 million. Many of those part-time jobs are, in fact, held by people working 38 or 39 hours a week.

If signed by the president, the new bill could have a major impact on big metro areas like Washington where government is the major employer, and more agencies are switching to flexible working hours that stretch out the workday, making part-timers essential to fill in gaps at the beginning and end of the regular eight-hour workday.

Although the bill would require agencies to begin working immediately to identify jobs that could be converted for part-timers, insiders say it will be two years before there is any dramatic increase in the number of jobs available to part-timers. The reasons for the delay are both mechanical and political.

The key to the bill is a changeover to a new accounting system so that agencies will not be penalized for having part-timers. Under the present system, a permanent part-time worker is counted as a full-time employe, even if he or she works only 16 hours a week.

Since part-timers and full-timers count the same in figuring employment ceilings, many managers have been reluctant to give up a full-time job slot for a part-timer. The change would allow agencies to count hours worked, so that two 20-hour permanent part-timers would show up as a single, full-time worker.

Backers of the original legislation, by Rep. Patricia Schroder (D-Colo.), wanted the earliest possible starting date for the new accounting system. But the Carter administration persuaded Senate-House conferees to delay the mandatory date of the new accounting system benefiting part-timers until Oct. 1, 1980.That is partly to give agencies more time to adapt to the new system. But there are also political reasons for the delay.

Carter was elected on a platform that called for a leaner, more efficient bureaucracy. As this column reported yesterday, his upcoming budget for the 1980 fiscal year (which begins in October 1979) is expected to ask an overall federal employment reduction of between 2 percent and 2.5 percent.

Officials feared than an earlier start on the part-time job program could be used by political opponent of the President in 1980. They could attack him for talking about smaller government while presiding over a big jump in employment. Those charges would not be totally accurate, since the big increase would be in part-timers.

Those chargers, while not be exactly accurate, could be made, and would be hard to defend. So the decision has made to delay the accounting change, which will encourage more part-time jobs, until October, 1980. Officials say agencies could proceed on their own in setting up part-time jobs. But they doubt many will be filled for two years.

Permanent part-time employment has jumped in the last two years, administration sources say, from 42,000 to 51,000. They say this makes better use of government salary money and provides more jobs. But many of those part-time positions are part-time in name only. A goodly number of them are filled by people working 39 hours a week, enabling agencies to say they are hiring more part-timers while getting the maximum hours out of each employe.

If the president signs the bill, the taxpayers will get a break on the cost of fringe benefits provided to future permanent part-timers.

The government now pays the same share of the employe health premium whether the worker is full-time or part-time. Under the new bill, part-timers hired in the future would have their government health premium contribution porated by the amount of time they work. Part-timers already on the payroll as permanent workers would not lose anthing. They will continue to get the same health insurance share payment as full-time workers.