The Church Society's evangelical.org site said the Rev. Rowan Williams would conduct the service at St. Peter's in London on Nov. 29, The Times of London reported Tuesday.
The list of those planning to attend was reportedly known only to Williams, the site said.
The society's general secretary, the Rev. David Phillips told the Times the service wasn't good for the Anglican Communion, already in disagreement worldwide over same-sex relationships and gay ordinations.
"The secretive nature and circumstances of the meeting suggest they have something to hide," Phillips said. "The archbishop might have defended the meeting with such a group on the grounds that he is engaged in a listening process. However, by leading the communion service he is clearly doing far more than just listening."
Coming off a three-month vacation, Williams is due to attend a meeting of U.S. Episcopal bishops this week to discuss the crisis begun in 2003 when openly gay Gene Robinson was ordained as a U.S. bishop.