Opposition Leader Bill Shorten has become the first Australian political leader to confront the Australian Christian Lobby on same-sex marriage, telling them he is a Christian who believes in marriage equality.

"I believe in God and I believe in marriage equality," he told the ACL national conference in Canberra.

"I believe in God and I believe in marriage equality": Opposition Leader Bill Shorten addresses the Australian Christian Lobby. Credit:Alex Ellinghausen

"I'm a Christian and a supporter of marriage equality under the law."

Religion should never be used as an instrument of division or exclusion, he said.