NEW YORK — A decision by organizers of the city’s St. Patrick’s Day Parade to allow one gay organization to march is a disappointment after decades of fighting by gay groups for full participation, several advocates said Wednesday.

Some were dismayed that the organizers had chosen just one lesbian, gay, bisexual and transgender group to participate next year after ending a ban on them. Others expressed continuing mistrust.

Nathan Schaefer, executive director of Empire State Pride Agenda, called the announcement “disappointing and self-serving.”

“While this development is long overdue, inviting one group to march at the exclusion of all others … is a far stretch from the full inclusion we deserve,” Schaefer said.

Sarah Kate Ellis, president of the gay-rights group GLAAD, said parade organizers — who announced other gay groups could apply for the parade in 2016 and afterward — “must be held accountable” to that pledge.