The Government Accountability Office is preparing to issue a report that rebukes the Centers for Disease Control and Prevention for saying in 2004 that elevated levels of lead in the District’s tap water did not pose a public health threat and for failing to quickly clarify its findings as complaints mounted.

The CDC has taken incremental steps to clear up public confusion and address flaws in the analysis. But as of January, the nation’s premier public health department had not published a definitive overview of how elevated levels of lead in tap water can harm children, the report says.

The GAO report, “Lead in Tap Water: CDC Public Health Communications Need Improvement,” was obtained by The Washington Post and is expected to be released about April 13.

It calls on the CDC to publish an article that divulges all it knows about the dangers of lead in drinking water and explain the health risk to children. It also urges the agency to develop procedures to review previously published information and determine whether clarifications or corrections are needed to better inform the public.

Lead is considered to be a toxin that cannot be consumed safely, especially by young children. Lead poisoning can diminish a child’s intellectual development and lead to hypertension in adults.

After tap water in thousands of D.C. houses tested above the federal limit for lead contamination, frightening residents and especially parents, the CDC published its analysis, playing down the health risk.

A congressional subcommittee determined in May that the CDC had made “scientifically indefensible” claims that high lead levels in the water were not causing noticeable harm to city residents.

Thomas R. Frieden, the CDC’s director, called the uproar after the article “painful.” In an opinion piece written last year, shortly after he was appointed to head the agency, he took issue with a section of the article that said no children had been identified with elevated blood lead levels, even in homes with the highest lead concentrations in water.

“I concluded that, in its urgency to rapidly assess the situation, the CDC communicated scientific results poorly,” Frieden said. “The CDC’s report left room for misinterpretation and may have led some people to improperly minimize concerns about lead exposure and conclude that lead in the water had never been a problem.”

A CDC spokeswoman declined to comment Friday on the GAO report, except to say that a draft had been received by the Atlanta-based agency and reviewed. The spokeswoman, Bernadette Burden, said the agency could not address the findings because the report had not been released.

However, the report says the CDC accepted its recommendation to prepare an overview that clearly explains the effects of lead. But the CDC agreed to only a portion of the second recommendation, saying it would establish a procedure for correcting articles but stopping short of a review of past articles.

“The CDC needs to take the GAO’s recommendations to heart,” said Rep. Brad Miller (D-N.C.), former chairman of the House subcommittee that investigated and criticized the CDC’s analysis.

“They need to set the record straight about what we know and don’t know about lead in tap water and what it does to people, especially to children,” Miller said. “And they need to make sure that they act quickly in the future when there is obvious confusion about their findings or they get new information regarding the [2004] report.”

Marc Edwards, a professor of civil and environmental engineering at Virginia Tech University, said the 2004 report “was used in a harmful way” because the CDC refused to correct the record. “If anyone can force them to look at these mistakes and correct them as soon as possible, it’s in everybody’s best interest,” he said.

In December, the CDC issued an internal report that said the water supplied to 15,000 homes in the District might still contain harmful levels of lead despite partial replacement of lead pipes from 2004 to 2008.

Even though exposure to lead in the District is minimal and the city meets the government safety standard, some children may still be getting troubling amounts of lead from drinking tap water.

For the study, scientists examined routine blood lead tests on 64,000 District children from 1998 to 2006. Nearly 20 percent were at risk of lead-induced health problems, according to the study.