By Todd Zwillich

WASHINGTON, Mar 28 (Reuters Health) - Animal cloning experts and bioethicists Wednesday attacked the handful of scientists and religious groups claiming to be on the verge of attempting to clone a human being, saying that such research is premature, unethical and nearly certain to produce abnormal babies.

Researchers told members of a House investigational subcommittee that the cloning technology that has been used to create genetic copies of pigs, cows, sheep and other animals is too new and unrefined to support the safe cloning of humans.

Scientists have recently expressed alarm that current cloning procedures have only a 3% to 5% success rate and that animals that do survive are prone to lung defects, heart anomalies, immune dysfunction and other problems.

Dr. Mark E. Westhusin, a cloning researcher at Texas A&M University, told the committee that 37 recent attempts to clone cows produced only two live calves, both of which died.

Still, some groups claim to be pushing ahead with plans to clone humans, primarily as a way to provide reproduction for homosexual couples or heterosexual couples that have not had success with in-vitro fertilization (IVF). Human cloning is about "the freedom to make personal reproductive choices," said Dr. Brigitte Boisselier, the director of Clonaid, a company that she says has hundreds of volunteers waiting to participate in the first US attempt to clone a human.

Another group, a Canadian religious sect known as the Raelians, claim to be ready to clone a dead 14-month-old child in an attempt to replace the child for his parents.

Proponents say that they plan to carefully screen all cloned embryos to prevent implantation of genetically defective embryos into human mothers.

"Comprehensive screening, although expensive, would ensure that only healthy, developmentally normal embryos would be conceived," said Dr. Panos Michael Zavos, the founder of the Andrology Institute and a member of an international consortium planning to clone a human within the next 2 years.

But other experts warned that ultrasound and other methods used for screening embryos in IVF wouldn't identify abnormal human clones. The cloning process usually results in gene reprogramming blunders that are undetectable by current genetic screening methods.

"Any of the 30,000 genes we have is a target for reprogramming errors. There is no way to screen for it with the available technology," said Dr. Rudolph Jaenisch, a professor of biology at the Massachusetts Institute of Technology.

Congress is contemplating banning human reproductive cloning research in the United States. Most researchers support the ban, but warn that legislation would have to be carefully crafted so as not to impede other, non-reproductive cloning research that could produce replacement cells for damaged human organs or tissues.

"Human cloning is a form of playing God since it interferes with the natural order of creation," said Rep. Cliff Stearns (R-Fla.).

Rep. John Dingell (D-Mich.) issued a statement urging caution as Congress addresses human cloning "because a clumsy, ideologically driven effort would chill or curtail some of the most important research being conducted in the life sciences."

A wide range of groups, including the American Medical Association, the Catholic Church and the United Nations General Assembly, have called for a ban on human reproductive cloning. In 1997, the National Bioethics Advisory Commission issued a report calling for a federal ban on cloning by nuclear transfer.

The Food and Drug Administration has claimed to have the authority to regulate all human cloning research under existing law. The agency has said that it considers the research to be unsafe, and has warned that it would not grant approval for any human cloning research.