Hwang Woo-suk, the South Korean scientist who has pioneered human embryo cloning for medical research, resigned on Thursday from all his official positions after admitting that two of his laboratory staff donated their eggs for his work.

Following weeks of speculation about ethical standards in his research, the Seoul National University professor called a press conference to apologise for having lied about the procurement of human eggs for his experiments. At the time the collection of the eggs did not breach any laws.