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Two conservative lawmakers have backed out of speaking engagements at next week's National Tea Party Convention, the latest trouble for the gathering of tea party activists.

Reps. Michele Bachmann, R-Minn., and Marsha Blackburn, R-Tenn., both prominent backers of the tea party movement, announced Thursday they won't attend the Feb. 4-6 event in Nashville, Tenn. Their offices released statements Tuesday citing concerns about how funds raised by the convention might be used.

Many tea party activists across the country are boycotting the convention because of its $550-a-person ticket price and the $100,000 speaking fee it is paying to Sarah Palin, the former Republican vice presidential nominee.

The convention is being run by a for-profit Tennessee corporation registered to Tennessee lawyer Judson Phillips, who has said he hopes to make money on the convention.

Dave Dziok, a spokesman for Bachmann, said in a statement to FoxNews.com that the congresswoman dropped out after receiving "conflicting advice" on whether her participation would be in line with the Committee on Standards.

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"There is uncertainty about how any proceeds from the event may be used, and we must err on the side of caution," he said. "Some will want to portray her withdrawal as repudiation of the tea party movement, but that couldn't be further from the truth."

Blackburn said in her statement that she told Phillips on Thursday that his company's for-profit status "has put many of his speakers in an awkward position."

"I remain encouraged by the outpouring of energy from constitutionally minded grassroots organizations in Tennessee and around America," she added.