One of the most prominent members of the Westboro Baptist church has left it after spending her life as part of the fervently anti-gay movement.

Megan Phelps-Roper, who looked after social media for the church best known for its slogan "God hates fags", announced her departure in a post on the blogging platform Medium in which she also revealed her younger sister Grace, 19, was also leaving.

In the post, called Head Full of Doubt/Road Full of Promise, the 27-year-old explained how she had become disillusioned with the teaching of Westboro, which is widely considered one of the most detested church groups in America for its "God hates fags" campaign.

Phelps-Roper writes: "We know that we've done and said things that hurt people. Inflicting pain on others wasn't the goal, but it was one of the outcomes. We wish it weren't so, and regret that hurt.

"We know that we dearly love our family. They now consider us betrayers, and we are cut off from their lives, but we know they are well-intentioned. We will never not love them.

"We know that we can't undo our whole lives. We can't even say we'd want to if we could; we are who we are because of all the experiences that brought us to this point. What we can do is try to find a better way to live from here on. That's our focus."

The Westboro Baptist church gained notoriety for demonstrating at military funerals across the US, claiming the Iraq and Afghanistan wars are God's punishment on America for tolerating homosexuality.

The church has a small congregation, largely made up of the extended family of the Reverend Fred Phelps, the grandfather of Megan and Grace Phelps-Roper. Their mother, Shirley Lynn Phelps-Roper, is one of its most outspoken representatives. In 2007 the BBC broadcast a documentary on the church by Louis Theroux, which was billed as The Most Hated Family in America.

As well as picketing military funerals, the church also pickets sporting events, concerts and other occasions in the apparent hope of publicity. As well as being anti-gay, it is also anti-Jewish, anti-Catholic and anti-Chinese.

In an accompanying Medium piece, Damsel, Arise: A Westboro Scion Leaves Her Church, Jeff Chu describes what led Megan, who was named by the Kansas City Star as "the future leader" of the church, to leave in November.

Chu writes that her ephiphany over Westborough's hateful dogma began with a Twitter discussion with Jewish blog Jewlicious's David Abitbol. She came to realise the problems with condemning people to death, arbitrarily fixating on the "sin" of homosexuality and believing that the church had all the answers.

The church told the Topeka Capital Journal that it did not know the whereabouts of the two women.