A bishop has become the first high-profile Catholic in England to withdraw support for Amnesty International after its decision to back abortion as a viable option for women who have been raped.

The Rt Rev. Michael Evans, Bishop of East Anglia, who had been actively involved in the human rights charity for 31 years, claimed he would be the "first of many" to cancel his membership after leaders voted overwhelmingly in favour of including access to abortion in their definition of human rights.

Evans, 55, said he was "very sad" at abandoning his work with the organisation.

"There are undoubtedly many Catholics who will now sadly have to withdraw membership. Bishops, priests and lay people will have to make a very serious decision about their memberships, and I would expect them to make the same decision.

"The question of abortion is so central to Catholic opinion that it will make it difficult for Catholics to remain involved. I feel I cannot continue, and I know from people writing to me that others have already done the same. But individuals need to decide for themselves."

His decision will enrage pro-choice and women's rights activists who believe the right to abortion for women should be fundamental.

Mike Blakemore, a spokesman for Amnesty, yesterday defended the change in stance.

"The policy is not pro-abortion, but it allows women to make a decision about their sexual health free from coercion, discrimination and violence," he said.

"We recognise the protection of the foetus as inseparably linked to the right to health and life of the mother."

Rather than forcing people to turn their back on the charity, Blakemore said, the move had attracted a rash of new members who agreed with its stance on a woman's right - albeit in certain extreme circumstances - to choose.

"The messages we've had from people around the world have not suggested that will be the case.

"We are an organisation that supports freedom of expression for everyone, so we respect their decision, but there are several Catholics who have chosen to stay with Amnesty."

The policy change - affirmed at a meeting of senior international Amnesty representatives in Mexico this month - had been awaited with trepidation by Catholics around the world.

The Vatican had already warned that it would expect believers to snub the charity if it reaffirmed the stance.

Earlier in the month, Cardinal Renato Marino, head of the Pontifical Council for Justice and Peace, said: "If, in fact, Amnesty International persists in this course of action, individuals and Catholic organisations must withdraw their support."