The Federal Trade Commission yesterday unanimously enacted a new rule to protect consumers from credit abuses in small loans and installment sales.

Yesterday's action, a culmination of eight years of study and testimony, incorporated revisions requested by the commission last month and a compromise proposed by Commissioner David Clanton.

Some of the key provisions of the rule prohibit creditors from seizing basic household items, from collecting any portion of a debtor's paycheck without going to court, and eliminate waivers designed to guarantee the creditor will win any suit against the debtor.

It also forbids the use of most household items as collateral and requires creditors to make a full disclosure of obligations to cosigners of loans and installment plans.

The FTC did not prohibit creditors from contacting friends and relatives of the debtor or bar companies from taking all goods bought on credit if a customer fails to make payments on the first of the purchases.

Commissioner Michael Pertschuk expressed disappointment that these two prohibitions were not included in the rule but said "consumers enjoyed a major victory today."

Commissioner Patricia P. Bailey, who also said the rule was not as strong as before the latest revisions, said, "It is still a rule which will protect consumers from the most abusive uses of credit remedies.

"The (provisions) we dealt with today are used mostly to harass and terrorize consumers," she said.

The rule, which will affect finance companies and retail creditors, will impact mostly on low-income consumers and those who become ill or lose their jobs and cannot make credit payments, Bailey said. She said some estimates show up to 60,000 people a year will be affected.

The rule met strong oppostion last month from Reagan administration appointees, George Douglas and Chariman James C. Miller III, but revisions made since June and Clanton's compromise made the rule acceptable to him, Douglas said.