A doctor working full-time at a Veterans Administration medical center in Texas earned $75,907 from the federal government last year--and $91,829 on the side.

His outside earnings were at the high end of the scale for VA doctors, but he was hardly alone. Last year 1,576 full-time VA doctors reported earning a total of more than $10 million through moonlighting, usually at a medical school or in their private practice, according to confidential VA records.

The doctors are allowed to earn an unlimited amount of outside income as long as they "satisfy their primary obligation--full-time VA service" and avoid conflicts of interest.

But the amounts that some of them are earning have raised questions about whether they are working full-time for the government. And some federal officials also are concerned that VA doctors who teach at the 134 medical schools affiliated with VA hospitals could be improperly influenced by the schools.

The federal government's Office of Government Ethics was the first to question the fees that VA doctors reported on their annual financial disclosure forms. In 1981 it asked the VA's inspector general to investigate, but a report has not been issued.

In the meantime, agency officials have played down the doctors' outside earnings, in part because they are afraid that a crackdown would make it more difficult to recruit and keep physicians.

Keeping doctors has been a problem for nearly all the agencies that hire them, but particularly at the VA, which operates the largest hospital network in the country and employs 11,398 doctors, both full and part time.

In March, the VA released a study showing that its full-time doctors earn $25,300 a year less than the average for their peers in private practice. For some specialties, the report said, it took the VA an average of 23 months to replace a doctor--despite pay incentives that can push a specialist's starting pay from the government up to $80,000 per year.

Charles V. Yarbrough, director of management support for the VA's Department of Medicine and Surgery, said the agency is "concerned" about the outside pay that its doctors collect. But, he said, it never has formally cautioned or disciplined a physician about his outside pay, and doesn't intend to.

"It's really not that big of a problem when you look at the total picture," Yarbrough said.

In 1981, 1,483 of the agency's 6,932 full-time doctors reported outside earnings under $20,000. Another 63 earned between $20,000 and $30,000, and 30 earned more than $30,000.

Yarbrough said he is confident that if the VA investigated the doctors' outside earnings it would find that the payments were proper.

For instance, he said, many VA doctors are the only specialists in rural areas, and if they were barred from earning income during their off hours, their communities would be denied their services.

But all the doctors who received more than $30,000 in additional income lived in major cities, according to VA statistics.

Another VA report, marked "for sensitive eyes only," found that 71 of the 158 chiefs of staff at VA medical centers averaged $10,759 last year in outside income.

That finding surprised some VA officials because the medical director's job is considered one of the most demanding in the VA system. By law, a chief of staff must be a full-time VA employe and VA officials have told Congress the job can take up to 80 hours per week. The report found that one chief of staff collected $43,260 teaching at a medical center last year; four others collected more than $20,000.

Sanford M. Garfunkel, a hospital specialist on Yarbrough's staff, said that a VA doctor's outside earnings often enable him to continue working for the government, even though his federal salary is less than he could make in private practice.

But critics within the agency, who asked not to be identified, said that VA doctors receive benefits not available to private physicians, such as government pensions, more regular hours, 30 days of annual leave and government-paid malpractice insurance.

Congress has passed five special "base-pay" increases since 1975, which have pushed the beginning pay ceiling for VA doctors from $36,000 to $57,500 per year. It also has approved pay incentives that enable doctors to collect $22,500 per year in bonus pay based on their skill, tenure and responsibilities.

Those combinations have raised the average pay for VA physicians to $77,200 per year, making them the highest paid doctors in the government, when benefits are excluded.

Still, the VA loses 10 percent of its physicians each year--twice the rate of medical schools and a higher rate than other federal agencies.

On average, VA doctors quit after 7.2 years. One reason could be pay compression: a VA physician reaches his maximum pay after eight years. Another may be that 43.7 percent of VA doctors are graduates of foreign medical schools, and work for the VA until they can establish their credentials.

As a result, the VA has developed a complicated system of part-time doctors, some of whom work as little as one-eighth of their time for the VA.

Last year, the VA reported that 7,232 of its more than 11,000 doctors teach at medical schools, including 1,129 who are full professors. The ethics office has been concerned that these doctors might find themselves caught in conflicts between the VA and their school. Neither the VA nor the ethics office, however, could cite an example in which such a conflict had occurred.