AUGUSTA — Maine’s secretary of state said Thursday he plans to file a formal complaint to stop political fund-raising mailers he says could be mistaken for voter-registration forms.

“It’s terribly deceptive in my opinion,” said Secretary G. William Diamond, adding that he will file a complaint with the Federal Elections Commission seeking to halt distribution of the forms.

The mailers sent this month from the National Republican Senatorial Committee in Washington ask for $9 payments to process “Voter Address Confirmation Cards” that are enclosed.

“This card must be filled out and returned,” the forms say in large, bold-type letters that are also underlined.

Diamond, Maine’s top elections, said he is concerned that many people who receive the cards will think they must return them and money in order to register to vote.

Wendy Democker, a spokeswoman for the National Republican Senatorial Committee, said “it’s very clear what it (the message) is. It says right up front, the National Republican Senatorial Committee.

“It was very clear that it was a mailing from us. We were asking for nine dollars to do research, vote tracking and polling,” Democker said, adding that “there was every disclaimer imaginable to indicate to people that it was not an official voter registration card … that this was a voter data card for us where we ask for survey information to help with voter turnout for Republicans in key districts.”

“That’s all spelled out right there on the cover,” she said, adding the program was new and that it is “not atypical of fund-raising programs to require” that information be returned in order to meet budget deadlines.

Diamond, a Democrat, also noted that the mailers include disclaimers and that technically, they may be legal. But he said he is still concerned about confusion that they may be creating among voters.

Democker said no more than 500,000 mailers were sent out nationwide around July 19.

She could not specify to which states the mailers were sent or exactly how many were sent, but said that it was an “average mailing” and that the committee had not received complaints from any voters or other states’ officials.

Diamond said he learned about the forms from a Bangor resident who complained to his office.