Credit problems are the No. 1 source of consumer complaints to the Federal Trade Commission, FTC Chairman James C. Miller III said last week as he launched a campaign to make Americans more aware of their rights in seeking credit.

Solving debt problems, dealing with a bad credit history and establishing credit are the most common areas of consumer concern, said Anne P. Fortney, associate director for credit practices in the FTC's Bureau of Consumer Protection.

FTC officials said that seven out of every 10 Americans use credit cards or other credit to finance their educations, remodel homes, obtain small business loans, pay for home mortgages and medical bills or just shop for clothes on the weekend.

With some 700 million active accounts across the nation, the credit industry is a "significant" one, said Carol Crawford, director of the Bureau of Consumer Protection. The Federal Reserve Board recenty reported that total outstanding consumer credit increased at an annual rate of 18.9 percent for the first quarter of this year.

The complaint most frequently heard by the FTC is "I was turned down for credit, but I don't understand why," Fortney said.

Divorced or widowed women may have difficulty getting credit because they often have no credit histories. "Women write in and say they can't get credit, although they've been paying the bills for 20 years, because the accounts were in their husbands' names," Fortney said.

Since 1977, creditors have been required to keep credit files in both names of a married couple, but because that was not always the procedure in the past, a married woman may have no credit record of her own.

Recent college graduates with no credit history, a new job and a new residence also may have trouble establishing a credit rating. Fortney said that the former student "may be confused, being solicited, perhaps, by American Express, but being turned down by J. C. Penney."

"The reason is that different creditors have different standards," Fortney said.

Credit problems can occur because of either slow payment or nonpayment of past debts, or errors. The FTC said that inaccurate information frequently is held by credit bureaus, which gather information and sell it to creditors -- the ones who decide whether to grant credit.

For example, if a person with a good credit history moves from one part of the country to another, the credit bureau in the new location might not have any records of the consumer's past experience. The FTC recommended that a credit applicant notify creditors to examine records located elsewhere.

Sometimes mistakes are entered into computers, or when computer systems "talk" to each other to exchange information, accounts of people with the same name or similar names may get merged.

Credit histories, which can be used in making future credit decisions, are kept in the credit bureau records for seven years and bankruptices are kept on file for 10 years.

Fortney advised consumers planning to apply for a mortgage or other major credit to check their history at a credit bureau ahead of time to avoid problems in obtaining the loan. Under the law, credit bureaus must tell individuals what is in their file, and some will provide copies of the file, although that is not required by law.

Some credit bureaus may charge a fee for providing file information, but they must disclose this in advance. If an individual's request is within 30 days of receiving a credit denial, there is no charge for the information.

Besides using credit histories, most firms either have a scoring system -- which assigns points to factors such as length of employment, with the score determining whether credit is issued -- or rely on the judgment of a credit officer.

Fortney said that the final credit decision cannot legally be based on gender, whether someone is married or if some income is from alimony. Loan officers, however, legally have the leeway to make a subjective decision that someone is a bad risk.

In addition to its consumer education campaign, the FTC is "testing" credit firms by sending people to apply for credit using nearly identical information, with only one difference between applications. The commission then is examining those credit decisions to see whether they are based on legal or illegal criteria.

Consumer credit problems have exceeded even used-car complaints, the agency said. In 1984, the FTC received 16,302 complaints from consumers, of which 4,400 or 27 percent involved credit problems.

And the complaints are only the tip of the iceberg, the agency said, because most people who have problems with creditors don't contact the federal government for help or answers.

The FTC, which enforces the Equal Credit Opportunity Act and the Fair Credit Reporting Act, has issued a series of free brochures offering advice on how to deal with credit problems. The pamphlets are available through the agency's Public Reference Branch in the District.