Mr Walker was National Director for Prison Fellowship England and Wales from 1992 to 2007 before joining Prison Fellowship International.
His voluntary experience includes the role of Chairman of a Christian Counselling Centre in Essex; a member of the leadership team and Chairman of Trustees for his local church; and with his wife, a pre-marriage mentor for couples preparing for their future together.
"I am greatly looking forward to taking up this position and the challenge to bring hope to those whose lives are affected by leprosy," he said.
"I join a dedicated team of staff and volunteers and respect their wealth of experience, commitment and passion to the cause of TLMEW. It will be a pleasure and a privilege to serve alongside them."
Reflecting on the most exciting things he witnessed in the prison environment, Mr Walker commented: "Seeing men and women in prison coming to faith in Christ always moved me. Helping them grow and mature in Christ and then supporting them on release are big challenges, but seeing the changes in their lives causes me to give much thanks to God.
"On a wider scale, I have been excited to be part of what God is doing through Prison Fellowship ministries around the world, reaching the prisoner, the ex-prisoner and prisoners' families."
Peter replaces former TLMEW National Director, Rupert Haydock who died unexpectedly on September 1, 2010.