The Southern Baptist Convention has voted to lift the lid on confidential documents in an investigation into its handling of sexual abuse allegations over the last two decades.

The denomination's Executive Committee voted 44 to 31 to waive attorney-client privilege in the investigation being overseen by Guidepost Solutions.

Tuesday's vote means that investigators can review private communications between SBC staff, members and lawyers.

The plan was approved despite opposition from some who warned it could nullify the denomination's insurance or compromise its "spiritual fiduciary duty."

But over 1,100 SBC pastors and leaders have supported the move, saying in an open letter last month that a "full, thorough, independent investigation" into the handling of the allegations "necessitates" waiving attorney-client privilege in order to "engender trust" in the denomination and "show Christ-like love to victims of sexual abuse".

The decision on Tuesday follows a lengthy debate in the Southern Baptist Convention and overturns two previous votes retaining attorney-client privilege. 

Addressing the Executive Committee, SBC President Ed Litton prayed for healing and "what needs to be exposed."

He also called for unity as he admitted that the denomination faces "a very uncertain future."

"We have all faced a very difficult and challenging time," he said. "We know the cost that has been explained to us again and again."