The Boy Scouts of America has lost 6 per cent of its membership after a year in which it announced it would accept openly gay boys for the first time.
The century-old organisation is facing a long-term challenge to stay relevant.
BSA spokesman Deron Smith said his organisation already recorded a 4 per cent membership decline between 2011 and 2012, with similar annual declines during the last decade.
The organisation's national leadership voted in May to accept gay boys, while continuing to exclude gay leaders.
That angered conservatives and some members who consider homosexuality a sin and a violation of Scouting values.
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Smith said on Wednesday that the 2013 decline could partially be attributed to that change.
"There are many factors that go into a family's decision to join Scouting, and it's impossible to point to any single factor that influences our membership numbers," Smith said in an email.
"This includes, but is not limited to, the limited amount of discretional time and parents wanting relevant programs for their kids."
With nearly 2.5 million youth and almost 1 million adults, Scouting remains a significant force in communities across the United States, even though its membership has slowly but steadily declined over the last decade.
BSA made the change to accept openly gay youth as it faced mounting public pressure in a nation that is growing more accepting of gays and gay marriage.
Zach Wahls, an Eagle Scout who founded the advocacy group Scouts for Equality, said he's heard of no incidents of potential discrimination since the policy went into effect.
He said suggestions last year of a mass exodus due to the policy change appear to have been overblown.
