The Mormon church has waded into the California gay marriage row calling on its members to join the effort to amend that state’s constitution to define marriage as being between a man and a woman.

A letter sent to bishops of The Church of Jesus Christ of Latter-Day Saints and signed by church president Thomas S Monson will be read out during church services this Sunday, reports The Salt Lake Tribune.

In May, California’s Supreme Court overturned a voter-approved ban on same-sex marriage, saying gays could not be denied marriage licences.

Mormon teachings on the issue “are unequivocal.”

In a statement, the LDS said:

“Marriage between a man and a woman is ordained of God, and the formation of families is central to the Creator’s plan for his children.

“We ask that you do all you can to support the proposed constitutional amendment by donating of your means and time to ensure that marriage in California is legally defined as being between a man and a woman.

“Our best efforts are required to preserve the sacred institution of marriage.”

The Californian Mormon congregation number almost 750,000 and have heard, and heeded, similar calls from their leaders in the past.

In 2000, a letter from the pulpit asked members to give time and money in support of Proposition 22, a ballot measure prohibiting California from legally recognising gay marriages performed outside the state.

But soon after Proposition 22 passed, the California legislature passed a domestic partnership bill that granted all the rights of marriage through civil unions.

As recently as 2006, the LDS signed a letter to Congress seeking an amendment to the US Constitution that would define marriage as being between a man and a woman.

This latest letter is a disappointment to members of Affirmation, an international support group for LGBT Mormons, who are due to meet with Fred Riley, LDS commissioner of Family Services, in August for the first time.

Last month, Affirmation called on the church not to meddle in California politics.

Executive director W Olin Thomas said:

“This initiative will hurt so many people. The California law affects civil marriage; it has no effect on any religious institution or official.

“Without marriage, a couple who have been together 30 years could be torn apart at the doorway to the emergency room.”

The meeting was meant to bridge the divide between Mormonism and gay members hurt by church teaching against the ‘sin’ of homosexuality.

However the group’s spokesman David Melson said:

“We’re not going to let this stand in the way.

“The church has said they are open to finding new avenues and new solutions to minister to gay members, and we are taking them at their word.”