More than 2,000 primary and secondary faith schools in England and Wales have been told they should no longer belong to or raise funds for the human rights organisation Amnesty International because of its new stance on abortion.

The Roman Catholic bishops of England and Wales wrote today to all Catholic primary and secondary schools advising them that membership or affiliation to Amnesty International has become "very difficult" because of the organisation's decision this summer to back the decriminalisation of abortion. They said they should no longer belong or be affiliated to Amnesty groups, and must also stop raising money for Amnesty.

Amnesty International, founded in 1961 by Jewish-born Catholic convert Peter Benenson a convert to Catholicism who died just two years ago, criticised the letter as "disappointing" and insisted there was still more than united Catholics and Amnesty than divided them.

Amnesty currently has 570 local groups in England and Wales, of which 81 are in Catholic schools.

All 2,323 Catholic schools and 16 Catholic sixth form colleges received the letter, in which the Archbishop of Birmingham, the Most Rev Vincent Nichols, head of Catholic education and Bishop Crispian Hollis, chairman of international affairs, urge them to continue to battle for human rights but through channels other than Amnesty.

In their letter they say: "We are writing to you in response to questions raised by a number of Catholic schools and parishes after the decision made by Amnesty International this summer regarding access to abortion.

"At the heart of our common Christian life and witness lies a passionate commitment to bring the Good News of God’s justice to the poor, the vulnerable and the oppressed of our world. We believe God demands justice, does justice, and promises justice. We believe God calls us to ‘do justice’ in his name. Religious education in our Catholic schools and parishes should always include a thorough presentation of the social teaching of the Catholic Church, as an inspiration to work together for justice here and now."

The bishops say that as Catholics, they continue to share the vision of Amnesty's original mandate, as well as its opposition to violence against women. "We acknowledge the vital work carried out by Amnesty over the years," they said. "However, any undermining of the fundamental right to life from its defenceless first beginnings is too important to be ignored."

The bishops acknowledge that Amnesty is not planning to campaign for access to abortion as a general human right. But they say: "Its new policy does involve upholding the right to access to abortion in certain circumstances, and thereby compromises the fundamental right to life."

Alternative groups that schools can support include Action by Christians against Torture, and other new groups currently being developed in the wake of Amnesty’s change of policy.

The bishops say: "It is essential that Catholic schools and parishes remain actively committed to their work for justice by putting into practice the social teaching of the Catholic Church, and to further developing effective ways to work for justice and human rights for all God’s people. "