The letter hit Harper's desk during the G8 and G20 summits, just weeks after Canada participated in a UN review of the Nuclear Non-Proliferation Treaty and two days before Harper announced a new nuclear co-operation deal with India.

"(The letter to Harper) is the best statement I've seen from a religious group. I can only say that I hope the government will listen intently," said Doug Roche, Canada's former ambassador to the United Nations on nuclear disarmament. "This statement is excellently timed to encourage, to spur, the government of Canada to become active in the new worldwide campaign for a nuclear weapons convention."

Canadian Conference of Catholic Bishops president Bishop Pierre Morisette of signed the letter on behalf of Roman Catholics. Metropolitan Archbishop Lawrence Huculak of Winnipeg added his name on behalf of the Ukrainian Catholic Church in Canada. Twenty-three senior church leaders, representing the entire Canadian Council of Churches, put their names to the letter.

It's the first ecumenical statement on nuclear weapons from the council since 1983. The letter gives both religious and secular reasons for abolishing nuclear weapons.

"We are called to love our enemies, and we are convinced that this cannot be accomplished through the build-up of nuclear arsenals. Nuclear weapons have only one capacity, and that is for mass, indiscriminate destruction with a power so great that it threatens the very existence of the human community and the environment that sustains it," said the letter.

Church leaders rejected strategic and security reasons for possessing nuclear weapons as "spiritual and moral bankruptcy."

"We cannot accept as defence any measures which threaten the planet itself."

The Canadian ecumenical statement follows the Vatican's own address to the NPT review in New York. At that meeting the Vatican's UN representative Archbishop Celestino Migliore quoted Pope Benedict XVI urging world leaders to "overcome the burdens of history and to weave patiently a political and economic web of peace in order to foster integral human development and the authentic aspirations of peoples."

Now that Harper has played host to the world's leaders at the G8 and G20 Summits, it might be a good time to re-assert Canada's historic opposition to nuclear weapons, said Pax Christi — Toronto spokesman Deacon Steve Barringer.

"New connections have been made that it might be possible to exploit," Barringer said. "We're talking about re-establishing Canada's role as an arbiter rather than a participant in the fighting."

It's important that the Christian voice is united on the issue, he said.

"This is one where on principle we can all agree."

Part of the purpose of the letter is to call on Harper to more clearly define his government's stance on nuclear arms, said Project Ploughshares executive director John Siebert. Project Ploughshares is a peace and disarmament think tank started by the Canadian Council of Churches. The letter to Harper is based on its research.

The Canadian Council of Churches hopes to get ordinary Christians thinking again about the moral implications of nuclear weapons.

"We hope it will provide a platform for our work in coming years," Siebert said. "There are places and ways that we're going to try to re-animate this discussion."