Saddleback Church Pastor Rick Warren has added his voice to a campaign against a California bill on assisted dying.

California Senate Bill 128, also known as the End of Life legislation, gained momentum from the case of Brittany Maynard, who was diagnosed with a terminal condition and moved from California to Oregon, where physician-assisted suicide is legal, to hasten her death.

However, Church leaders have widely opposed its introduction in California. Speaking at a panel event, Warren – whose son Matthew committed suicide aged 27 in 2013 – warned hearers not to be apathetic about the legislation.

"I oppose this law as a theologian and as the father of a son who took his life after struggling with mental illness for 27 years," he said.

He gave examples of cases in the Bible where Moses, Elijah, Jonah and Job begged God to take their lives. However, he said, God had different plans for them. "The prospect of dying can be frightening," he said. "But we belong to God, and death and life are in God's hands. We need to make a radical commitment to be there for those who are dying in our lives."

Among others resisting the proposal is the Roman Catholic diocese of Orange, which said in a document outlining its position: "The claim to a right to assisted suicide raises many questions, not the least of which is this: if there is a 'right to assisted suicide', why would such a right be restricted only to those in the throes of terminal illness? What about the elderly person suffering a slow but non-terminal decline? What about the adolescent or young adult in the throes of depression, demoralization, or despair? What about the middle-aged man who is alone and simply tired of life?"

The diocese added: "While laws may initially erect fences around the practice of assisted suicide – having six months to live, being over the age of 18, having mental capacity, etc – these 'safeguards' will eventually be unmasked as arbitrary."