Leslie currently serves as:
- Vice President of the International Society of Empirical Research in Theology
- Vice President of the International Seminar on Religious Education and alues
- President of the Rural Theology Association
- Chair of the Alistair Hardy Trust.
He is also a member of:
- American Psychological Association
- Association for the Sociology of Religion
- British Educational Research Association
- British Psychological Society (Fellow from 1988)
- British Sociological Association (Sociology of Religion Study Group) Christian Education Movement
- College of Preceptors (Fellow from 1994)
- Education and Ethos Network (Board member since 1997)
- International Academy of Practical Theology
- International Association for the Psychology of Religion
- International Seminar on Religious Education and Values National Advisory Panel for Religious Education (Chair since 2005)
- Network for Psychological Type and Christian Faith (Co-convenor since 2002)
- Network for the Study of Implicit Religion (Trustee since 2002)
- Religious Research Association
- Social Research Association
- Society for the Scientific Study of Religion.
