A music festival is facing increasing pressure to end its exclusion of transgender women, a practice that critics call discriminatory.

For the past 38 years, the Michigan Womyn's Music Festival, often called Michfest, has served as an idyllic gathering in the woods for women to bond and celebrate. Thousands gather to briefly revel in a matriarchy, to eat and live communally and attend concerts and classes -- all conducted by women. This year's gathering begins August 5 on a piece of land in the western Michigan wilderness. But controversy has marred the fest and its founders, gathering steam in recent years, over its intention that only "womyn-born womyn" attend the event.

On Monday, LGBT advocacy group Equality Michigan released a petition calling on Michfest to end that practice, artists and attendees to boycott the festival until discrimination is stopped and for founder and organizer Lisa Vogel to meet with leaders of the transgender community. By Tuesday it had gathered 350 signatures. Equality Michigan intends to deliver the petition to the festival organizers, as well as vendors and performers who participate in it.

"The reality is that the lesbian, gay, and bisexual community cannot stand by any longer and pretend that any form of transgender discrimination can be painted over as a feminist or progressive issue," the Equality Michigan team wrote in a letter introducing the petition. "We must stand up, even if it is to our own, and make it clear that transgender women deserve to be treated as women in all settings. ...The time has come, we are drawing a line in the sand, this 'intention' can no longer stand."

Equality Michigan Executive Director Emily Dievendorf said the organization has been following Michfest for years and spoken against its stance on trans* women -- trans* is an inclusive term that refers to all identities along the gender identity spectrum -- but this year marks a stronger response. "We weighed in on Michfest this year because it has been decades now of hearing the same false claims and scare tactics to justify the alienation of trans* women and every day of those decades along the way was too long to wait for love and support to emerge for our trans* sisters in the women's movement," Dievendorf said in an email to The Huffington Post.

The conflict plays into the clash between transgender politics and certain strains of radical feminism that see the oppression faced by "women born as women" as different -- and worth separating from -- the struggles of transgender women. Some go further and dismiss transgender individuals more resolutely: a recent New Yorker article dealing with the divide quotes Sheila Jeffreys' book "Gender Hurts," in which the feminist author says, "Use by men of feminine pronouns conceals the masculine privilege bestowed upon them by virtue of having been placed in and brought up in the male sex caste."

The New Yorker article traces the fight to the '70s, when Michfest was started and there was a swell of like-minded groups and events. Such an exclusionary view of transgender women is becoming less and less tolerated, or seen as increasingly transphobic, in feminist circles and more widely as trans issues gain recognition.

Vogel has insisted that Michfest's intention to limit participation to "women born as women" is not a policy, but a self-enforced intention and "respectful feminist statement" that attendees could interpret or follow as they wished. This year, the festival will hold an "Allies in Understanding" workshop to discuss the issue.

In May, Vogel wrote that the festival has always "been a welcoming space for revolutionary womyn and girls who personify a broad spectrum of gender."

We have said that this space, for this week, is intended to be for womyn who were born female, raised as girls and who continue to identify as womyn. This is an intention for the spirit of our gathering, rather than the focus of the festival. It is not a policy, or a ban on anyone. ...We do not and will not question anyone's gender. Rather, we trust the greater queer community to respect this intention, leaving the onus on each individual to choose whether or how to respect it. Ours is a fundamental and respectful feminist statement about who this gathering is intended for, and if some cannot hear this without translating that into a "policy," "ban" or a "prohibition," this speaks to a deep-seated failure to think outside of structures of control that inform and guide the patriarchal world.

Dievendorf, however, rejected Vogel's claims, saying that a statement that asks women to keep silent about their true identities can't be considered open.

"The claim that transgender women are able to safely attend, while documented cases of transgender women being escorted out continues to occur, is similar to the military's statements around their 'Don't Ask, Don't Tell' policy [that allowed gays to serve only if they were in the closet]," Dievendorf said.

In an op-ed for Between the Lines, Zoe Steinfeld wrote about the feeling of being excluded from a festival meant to be a refuge for women.

"We're not demanding they let us in, but that they stop pushing us out," she wrote. "We're not invading women's spaces with men's bodies, we're women banished from our own spaces. ...To judge [a marginalized woman] an outsider based on a violent patriarchal system of sex assignment is not feminist. To echo conservative paranoia about her isn't progressive. To attempt to speak in her stead -- by wearing a t-shirt and attending a workshop -- while paying to enjoy the institution that silences her, isn't allyship."

In May, actress Lea DeLaria, who plays Big Boo on Netflix show "Orange is the New Black," canceled her planned performance at the festival after receiving criticism online, with some pointing out that her OITNB costar Laverne Cox, as a trans actress, would be barred from attending.

Several other performers have severed ties with the fest, most notably festival mainstays the Indigo Girls, who said last year that it would be their last time attending until organizers made significant progress toward changing the policy.

"I truly look forward to the time when all LGBTQ stand as one," DeLaria told the Advocate. "Perhaps then we can collectively laugh at how f****d up is it when I'M the voice of reason."

UPDATE: July 31, 11:00 a.m. -- On Wednesday, national LGBT advocacy organization the Human Rights Campaign also came out against Michfest's exclusion of trans women.