Seoul, South Korea (LifeNews.com) -- A University of Pittsburgh scientist who had been a key partner and leading apologist for the embryonic stem cell research and human cloning activities of a team of scientists in South Korea has quit.

He says the research team is involved in ethical problems relating to how it obtains human eggs from women for its studies.

Gerald Schatten, director of the Pittsburgh Development Center and a medical
school professor released a statement Saturday saying he was ending his partnership with human cloning scientist Hwang Woo-Suk.

According to an AP report on the statement, Schatten cited reports written last year in the scientific publications Science and Nature. The articles raised ethical questions including an allegation that some of the donated eggs for research came from one of the female scientists.

"My decision is grounded solely on concerns regarding oocyte donations in Dr. Hwang's research reported in 2004," Schatten said. He said he still believes in the promise of Hwang's research, which has drawn criticism from pro-life advocates.

Hwang has previously denied any ethical breaches and said the researcher in question has said she would be willing to donate eggs to other scientists for other studies.

Schatten said that "regrettably, yesterday information came to my attention suggesting that misrepresentations might have occurred" on the egg donations, AP reported. He said he contacted academic and regulatory agencies about the problems.

In the Nature report, bioethicists interviewed said researcher should not have anything to do with the eggs used in experiments or even intimately know the subjects who donate them.

Schatten had been working with Hwang's team for about 20 months and was slated to head the board of directors for the stem cell bank.

Arthur Caplan, a University of Pennsylvania School of Medicine ethicist who backs the controversial research, told Bloomberg News that Schatten's departure may cast a shadow over Hwang's research and end any involvement in it by U.S. scientists.

"The international community will be backing away fast'' Caplan said in a telephone interview. "Cloning research is too controversial for people to get two or three strikes for an out.''

Last year, Hwang's team claimed to have cloned the first human embryos and, earlier this year, claimed to have cloned the first set of genetically matching embryonic stem cells.

Hwang opened an international stem cell bank in October to donate embryonic stem cells to other researchers.