WASHINGTON (AP) _ Millions of automobile child restraint seats that have failed government standards are still being used or sold, a safety group said Friday. A top federal safety official denied the claim and urged parents to continue to use the seats.

The Center for Auto Safety and parents of children killed or injured in allegedly defective child restraint seats blamed, in part, the National Highway Traffic Safety Administration for allegedly failing to issue recalls or enforce those it does issue.

''Children ride at risk because recalled seats are not replaced or repaired, warning labels are approved that never reach owners, investigations are dropped without recalls and compliance test failures are ignored,'' center director Clarence Ditlow told a news conference.

He said that more than half of the 27 million child car seats sold over the last eight years are ''in use despite being recalled or failing compliance tests.''

Jeffrey Miller, assistant NHTSA administrator, said, ''It is categorically false to suggest, as Mr. Ditlow does, that half the seats on the road are dangerous.''

He acknowledged that only 7 percent of seats subject to recalls are actually brought into compliance, but he said recall responses for all products are low and most of the 26 recalls issued over the last decade involve minor problems.

He said laws requiring child safety seats in all 50 states and the District of Columbia have pushed usage to 82 percent.

''Hundreds of children are saved each year and countless injuries are reduced or prevented altogether,'' Miller told a news conference called to respond to the center's report. Department analysts estimate that wide use of safety seats has reduced infant deaths in car accidents by about 70 percent.

Miller, and Ditlow, urged consumers concerned about the safety of child restraints to call the Transportation Department's auto safety hotline (800-424-9393) for information about any seat or a list of recalls.

The center's report said 622 children were killed while strapped into child safety seats in the last decade. The study did not break down how many children died as the result of unsafe seats, how many died from the improper use of the seats and how many died in accidents in which no amount of protection would have saved the child.

Among problems cited in recalls were belt fasteners that don't hold, belts that are too loose, buckles that pop open, seat shells that crack, seats that incline too far to hold the child and belt choking hazards.

A major child seat manufacturer, Evenflo, said through spokesman Bob Potter that some seats the center cited have been on the market for years, with millions sold, and have proved their safety benefit.

Potter said the company had complied with all government safety orders and all federal regulations, even going beyond government requirements in ensuring the safety of its seats.

The center study asked the Transportation Department to examine all deaths involving child restraint seats, to reopen several compliance cases against manufacturers and to increase enforcement of recalls.

Ditlow alleged that at least 8 million seats have failed safety compliance tests but were not investigated or recalled by the government, while an additional 3.4 million were investigated but not recalled. Of 5.6 million subject to recall, he said, only 300,000 were actually replaced or repaired.

The report maintained that many defective seats are still being sold by retail stores throughout the country.

The center director appeared with the parents of children who were injured or killed in seats the parents had thought were protecting their children.

Ditlow said all manufacturers have had safety problems. ''We cannot point out any single manufacturer that has a sterling record,'' he said.

Cory McKinley of Buffalo, Minn., whose 2 1/2 -year-old daughter, Nancy Ann, was killed in a September crash, said he found out after the accident that the seat the child was using had been the subject of a recall.

''They make us use them and then they don't work. It kind of makes us sick,'' McKinley said.

Louie Checcino of Fairport, N.Y., said his 1-month-old child, Kara, was partially paralyzed when she was thrown out of a recalled seat.

The report said the center's six-month investigation found several cases in which the safety administration had failed to investigate child restraints that failed compliance tests, had dropped investigations despite manufacturers' failures to comply, had approved useless recall remedies or had failed to ensure that manufacturers notified consumers of recalls.

In a recall affecting 1.4 million Evenflo Dyn-O-Mite restraints earlier this year, the center said it could find no evidence that anyone had been notified, including retailers, who continued to sell the seat.

Potter, speaking for Evenflo, said the company had taken several steps to disseminate information about the recall, which involved attaching a warning label that the seat should not be used in its most reclined position if only a lap belt were used to fasten it to the car. Seats manufactured after the recall were altered to comply, he said.

In connection with the report, the center filed petitions with the safety administration to force replacement of the Dyn-O-Mite seats and the recall of 4 million Evenflo One Step child restraints, alleging inadequate crashworthiness and a defective latch that it said was involved in 15 accidents in which children had been killed or injured.

Other petitions asked the agency to require manufacturers to register purchasers' names and addresses and to prevent seat makers from using ineffective warning labels.