ROME – Scientists who carry out embryonic stem cell research and politicians who pass laws permitting the practice will be excommunicated, the Vatican said yesterday.

“Destroying human embryos is equivalent to an abortion. It is the same thing,” the head of the Pontifical Council for the Family, Cardinal Alfonso Lopez Trujillo, said.

“Excommunication will be applied to the women, doctors, and researchers who eliminate embryos [and to the] politicians that approve the law,” he said in an interview with Famiglia Christiana, an official Vatican magazine.

Excommunication forbids Catholics from receiving communion, assisting in any church duties, and sometimes from having a church burial.

But the threat was shrugged off yesterday by Italy’s leading expert on cloning, professor Cesare Galli of the Laboratory of Reproductive Technologies in Cremona, who was the first scientist to clone a horse.

Mr. Galli likened the Vatican to the Taliban and added: “I can bear excommunication. I was raised as a Catholic, I share Catholic values, but I am able to make my own judgment on some issues, and I do not need to be told by the church what to do or to think.

“I will be, together with Elena Cattaneo [a scientist working in the University of Milan], the first to be affected by the excommunication, and then there are two other labs that I know using imported embryonic stem cells.”

The research is opposed by the Catholic Church because it involves destroying embryos. This occurs at the point when they consist of about 100 to 200 cells and the so-called inner cell mass is removed. These stem cells can grow indefinitely and turn into any of the body’s 200 cell types.

Scientists believe research making use of the cells could eventually yield treatments for a range of diseases, including diabetes, heart disease, and Parkinson’s.

The Vatican’s tough stance on the issue came as the pope prepared to visit Valencia for the fifth annual world conference on the Catholic family. Spain passed a law permitting embryonic stem cell research two years ago to the dismay of the church.

An Italian senator, Paola Binetti, a member of Opus Dei and a prominent campaigner for Catholic rights, also spoke against the church’s line.

“I am upset and stunned,” she said. “It is a mistake to give out the idea that God is angry with man because he is not in agreement with him.”

Cardinal Trujillo said it was not just Spain that had “thrown out the fundamental laws of nature” but also Belgium, the Netherlands, the Scandinavian countries, and France. He did not mention Britain, which is at the forefront of embryonic stem cell research.