A D.C. City Council committee heard two witnesses yesterday assail a bill to prohibit unsupervised District drivers under the age of 18 from driving between midnight and 6 a.m.

The criticism came at a hearing on the bill, which would impose a curfew on licensed drivers under 18 in the early morning hours unless they are under the supervision of a licensed driver 18 or older.

Council member Nadine Winter (D-Ward 6), chairman of the Public Works Committee, which held yesterday's public hearing, said she introduced the measure because she was concerned that too many unsupervised youngsters are behind the wheel in the early morning. Based on statistics from states with similar laws, Winter said she was convinced that a driving curfew would reduce the number of accidents involving teen-agers.

"We have the right to protect the health, safety and welfare of a group of individuals we consider children," said Winter. "If we save only one life as far as I'm concerned it would be worth it."

But Wesley Watkins, executive director of the American Civil Liberties Union of the National Capital Area, testified against the bill, saying, "They have not demonstrated that this is a high-risk group . . . . They can't just arbitrarily take these rights away. Behind some of the curfew laws around the country, there is a general attitude that our society is out of control and that teen-agers are at the center of the problem. But there has to be some rational reason for singling out this group."

Robert O.D. Thompson, administrator for the District's Transportation Systems Administration and the only other witness to testify, said there is "not a significant problem" with drivers age 16 and 17 in the District.

A random sample conducted by the District's Department of Public Works showed that drivers under 18 represent less than 1 percent of all D.C licensed drivers involved in serious accidents between midnight and 6 a.m, according to Thompson. District records show that between the hours of midnight and 6 a.m., drivers under 18 were involved in 71 accidents in 1984 and 84 accidents in 1983, Thompson said.

The city has an estimated 400,000 licensed drivers, but city officials said they did not know how many are under 18.

Thompson also said that 13 percent of the District's 16-year-olds have licenses, compared with 46 percent nationwide, and that 28 percent of the District's 17-year-olds have licenses, compared with 70 percent nationwide.

Brian O'Neill, president of the Washington based Insurance Institute for Highway Safety, said in an interview, "There is solid research that shows that if the law is well-known and enforced, it does reduce crashes." He added, "Parents tend to be strongly in favor of the laws where they exist and tend to be the ones to enforce them. The laws give parents some extra leverage and control over teen-agers."

In a separate action yesterday, the City Council's Judiciary Committee voted to amend its child abuse and neglect law to include sexual exploitation and negligent treatment. The change is necessary for the city to qualify for grants from the National Center on Child Abuse and Neglect.