A former Maryland legislator who lost his seat in the primary election last September has collected $3,800 in unemployment benefits during the last eight months, even though state law specifically excludes elected officials from collecting unemployment insurance after leaving office.

Frank M. Conaway, a one-term Democratic delegate from Baltimore, filed for unemployment pay last January, claiming he was without work and entitled to assistance because of a "lost election."

Conaway, 50, officially lost his $18,000-a-year job when the new legislature was sworn in Jan. 12. Since then, he has received a weekly check of about $150 from the state. The payments stopped this week after embarrassed state officials inadvertently discovered them.

Conaway, who during his term authored bills to increase the payout from the state lottery and make peppermint lemonade the state drink, said yesterday, "I don't have any statement at all to make."

When asked whether he would reimburse the state he said, "I don't have any idea what you're talking about."

Conaway served as head of the House of Delegates Black Caucus until he lost his seat. His defeat followed grand jury and state investigations into his insurance business that ended when he decided to give up the business.

Maryland officials reacted to the news of Conaway's payments with outrage and surprise. House Speaker Benjamin L. Cardin, who learned of the matter last Friday, said, "It's wrong for anybody to collect unemployment illegally, but it is particularly troublesome when a public figure is involved. I would certainly like an explanation of what happened both in terms of why the payments were made and why he Conaway made the request in the first place."

Maryland Attorney General Stephen H. Sachs said he is investigating the matter and will take Conaway to court if necessary to get the money back.

State unemployment insurance officials yesterday declined to discuss the payments to Conaway. However, they said that Conaway will be asked to pay the money back.

According to Luther W. Starnes, a spokesman for the Human Resources Department, which oversees unemployment benefits, legislators, high-level appointed officials and judges, among others, are not covered by the state unemployment insurance law.

Maryland gave out more than $330 million in unemployment pay in 1982. About $5.4 million of that was given to people who, it was later learned, did not qualify for it.

In 1982 the state recovered nearly $3 million of those payments.

According to legislative officials, the Conaway matter only came to light last Friday when a member of the legislative accounting office casually mentioned it during a conversation with Janet Davidson, an aide to Senate President Melvin A. Steinberg.

The accounting official was complaining about the heavy flow of unemployment claims this year from members of the legislative staff, Steinberg said.

The accounting office provides salary and employment information to the unemployment division.

The official said that accounting was too overworked to thoroughly check all claims, checks that often required making a trip to the Baltimore headquarters of the unemployment division. As a result, the official said, some claims that should be scrutinized, such as one to a former delegate, were getting approved.

According to Steinberg, the accounting official did not realize that it was against the law for Conaway to collect unemployment. However, the accounting office did question whether legislators were covered on the form sent back to the unemployment division.

Officials in the human resources department, who asked not to be named, said yesterday that there are many temporary employes in the unemployment division, and it is likely that one of them approved the claim by Conaway without knowing that the law prohibits it.