Outgoing Empire State Pride Agenda head Alan Van Cappelle is taking a parting shot at openly gay Sen. Tom Duane — who he publicly called out by name to pass the gay marriage bill months ago — over a stalled transgender rights bill the state senator is sponsoring.

In an email missive aimed for wide distribution sent by a top ESPA official, the group paints Duane, the lone openly gay state senator, as the major holdup on passing the GENDA bill — suggesting as lead sponsor he is refusing to recraft some language to move it to a committee where it could get enough votes to move forward.

The email calls for people to “act now” and call Duane’s office, and claims an ESPA count shows there are 29 “yes” votes if it goes to the floor – nearly enough to pass it.

Last fall at ESPA’s annual dinner Van Cappelle – who is leaving to join City Comptroller John Liu’s senior staff — publicly named Duane in a fiery speech and urged him to help bring a gay-marriage bill to the senate floor, claiming he’d long promised the votes were there to pass it.

The bill ultimately did get introduced — only to fail in a lopsided “no” vote.

The GENDA email was seen by some as a tough public push on a key ally. But Van Cappelle said the bill has an 80 percent approval rating in polling done on it among New Yorkers.

“We have a prime sponsor of the legislation who spends a whole lot of time talking about it and who spends no time trying to talk to his colleagues about how to” pass it, he said, adding that Duane is a “trailblazer” in the gay community but that “people were less than impressed by his performance on the floor of the senate during the marriage vote and are concerned about his leadership on other issues.”

Duane couldn’t immediately be reached.