Rep. Patricia Schroeder (D-Colo.) has urged her colleagues to "go ahead and fire some" of their employees if they feel their staffs are too big, but "don't say you are doing it because of recent staff growth," according to a letter circulated to House members this week.

Schroeder said staff for the legislative branch has dropped 7.2 percent since January 1981.

In 1980, she said, Congress and all its branches and offices employed 39,969 workers. In 1986, the number was 37,299, and last year it rose to 38,061.

Schroeder's letter was in response to a Washington Post Outlook article published Jan. 17 with the headline, "Memo to Congress: Fire Half Your Staff."

"My point is not so much to focus on the absolute numbers as to look at the numbers vis-a-vis the executive branch," said Schroeder, who chairs the House civil service subcommittee. "In 1981 we had 14 staff members for every 1,000 in the executive branch, and today it is 12 1/2."

But Mark Bisnow, the former congressional staff member who wrote the Outlook article, dismissed the comparison as "irrelevant."

Bisnow said in his article that the number of personal, committee and administrative staff members had tripled since 1970. In an interview, he said his figures differed from Schroeder's not only because they covered a longer period but because they included only what he calls "core" staff -- excluding the General Accounting Office, the Congressional Research Service and the Office of Technology Assessment, which were counted by Schroeder.

Bisnow said the largest increases occurred in the 1970s in response to the Nixon presidency "when members of Congress felt he had tried to pull the wool over their eyes and they needed independent sources of information," and when subcommittees were increased and junior members of Congress were given more substantive responsibilities.

He said there has been a "little tapering off" of core staff growth in the 1980s.

Schroeder declined to endorse the need for 38,061 staff members. "There is always a way to do more with less everywhere," she said. "But the Reagan people do less with more."

She said she was "not particularly" pleased that the legislative staff totals increased last year by 762. "But we have to deal with the trend in the executive branch," she said.

"Nobody can question that Congress has broken down, that we've really got problems," Bisnow said. "Staff helped up to a point, but the numbers are counterproductive, people are at loggerheads.

"The services performed by the staff really do confer unfair advantages on incumbents" and the large congressional staff raises the issue of micromanagement, he said.

"It is not the responsibility of Congress to be looking into everything in the executive branch. Congress provides an important check on excesses but it is no joke when people talk about 535 secretaries of state and 535 secretaries of HUD.

"They have the staff to help them do it," he said.