(Reuters) - The first openly gay bishop in the Episcopal Church, whose election to lead the diocese of New Hampshire kicked off a firestorm of controversy a decade ago, said on Sunday he was divorcing his husband after four years of marriage.

Gene Robinson, who retired as a bishop in 2013, announced the split in a letter to the Episcopal Diocese of New Hampshire and in a personal essay published in the Daily Beast, where he wrote that his "belief in marriage is undiminished."

"It is at least a small comfort to me, as a gay rights and marriage equality advocate, to know that like any marriage, gay and lesbian couples are subject to the same complications and hardships that afflict marriages between heterosexual couples," he said.

Robinson's election in 2003 as bishop of the New Hampshire diocese stirred protest in the Episcopal Church, the U.S. branch of the worldwide Anglican Communion. Hundreds of parishes opposed to his consecration left the 2.3 million-member Episcopal Church, saying it was becoming too liberal.

The former bishop is now a senior fellow at the Center for American Progress in Washington.

He said details of his divorce from Mark Andrew, whom he married in 2010 when gay marriage was legalized in New Hampshire, would remain private.

"We ask for your prayers, that the love and care for each other that has characterized our relationship for a quarter century will continue in the difficult days ahead," he said in a statement to the Diocese of New Hampshire.

(Reporting by Victoria Cavaliere; Editing by Colleen Jenkins and Mark Trevelyan)