Attorney Mark Naugle said church members who want to resign brought the letters to his office on Saturday.
"We had an incredible turnout," he said. "I was slammed for three hours. Some people stood in line for an hour and a half."
Naugle said he plans to deliver the letters on Monday.
A call for mass resignations call started about a week ago
, when the LDS church released new guidelines for lay leaders known as "Handbook 1."
One policy prohibits the "natural or adopted" children of parents in same-sex relationships from receiving a name and a blessing in a ceremony performed by the Mormon priesthood, according to the handbook.
"The fact that it affects children really upset people," said Naugle, who is helping people resign from the church. "Most people are disaffected from the church already, and this was the final straw."
Naugle said he will deliver the resignation letters symbolically to LDS headquarters in Salt Lake City, Utah.
In a clarification issued Friday, the church said the policy does not affect children already baptized into the church.
"We don't want to see anyone leave the church," the LDS said. "We hope that today's guidance from church leaders and the additional commentary will help provide understanding and context to some who may be considering resigning their membership," according to CNN affiliate KUTV
Naugle said the church's clarification did not stop the resignation requests coming into his email inbox.
Church spokesman Eric Hawkins reaffirmed the church's longstanding opposition to same-sex marriage when the new guidelines were released.
"While it respects the law of the land, and acknowledges the right of others to think and act differently, it does not perform or accept same-sex marriage within its membership," the statement said.