After eight years of study, 250,000 pages of documents and 14,000 pages of testimony, the career staff of the Federal Trade Commission said it felt it had demonstrated convincingly that massive abuses in consumer credit practices required action by the commission.

But in a hot session made even steamier when the General Services Administration shut off the air conditioning in the FTC building, the career staff was told that their documentation was not enough. The staff was challenged by the two Reagan appointees--Chairman James C. Miller III and George W. Douglas--and the bureau chiefs Miller had put on the job.

With the help of Commissioner David Clanton, who will retire in September, Miller and Douglas blocked action last month on rules to police the consumer credit industry. The series of votes left the career staffers hanging, with only Commissioners Patricia P. Bailey and Michael Pertschuk supporting them.

It was a classic clash between career staff and political appointees and--unusually for Washington--it took place in full view of the public.

The second public round is set for July 20, when the career staff will try again with an amended set of rules designed to bring Clanton around to their point of view.

There is a fear among the FTC career staff, however, that the consumer credit rules have been stalled to death as a result of the month's delay. Even if they are approved this time around, it is unclear whether the rules can be promulgated before Clanton's term ends Sept. 25.

"The career staff people are the adversaries of the politically appointed bureau chiefs who are their bosses. The question is, will the political appointees let the papers come up or will they stall," said one FTC staffer.

Miller was reported by his staff to be concerned about the stalling charges and has insisted on speedy action.

The long, hot debate displayed the deep differences between commissioners, as Miller and Douglas press for a strict economic analysis on every issue. Their people in the staff hierarchy--Carol T. Crawford, director of the Bureau of Consumer Protection, and Wendy Gramm, director of the Bureau of Economics--faulted the staff recommendation for being based on anecdotes instead of rigid economic principles.

Bailey and Pertschuk challenged that conclusion. They argued that the anecdotal information that vividly illustrated the abuses of consumer credit practices were supported fully by economic studies. Pertschuck, FTC chairman during the Carter administration, termed some of the arguments raised by the other side as "surreal."

"Perhaps more than any proceeding in recent memory," said Pertschuk, "the commission's eight-year effort to restrain the harshest and most destructive debt collection practices poses a fundamental clash over the true nature of consumer behavior."

In a dig that angered Miller, Pertschuk quoted Massachusetts Institute of Technology economist Lester Thurow, saying that modern economic analysis adheres "slavishly to a 19th century model of consumer behavior which 'has long since been rejected by sociologists and psychologists who specialize in studying human behavior.' "

"Perhaps," said Pertschuk, "this is why much of the arcane and elaborate economic analysis which purports to demonstrate the benefit to consumers of the harsh and uncivilized collection remedies which this proceeding would restrict strikes the non-economist as surreal."

At one point, Pertschuk suggested that Adam Smith's economic theory had referred to debtors' prisons, which sent Miller to the library. After a quick check, Miller declared that Smith never mentioned debtors' prisons in his classic tract, "The Wealth of Nations."

That may have been the only point that was firmly settled at the FTC meeting.