Jan. 27 (Bloomberg) — A Republican group promoting pro- business candidates as it battles the Tea Party in U.S. primary campaigns is being financed mostly by labor unions, one of the Democratic Party's staunchest allies.

Defending Main Street, a super-political action committee aligned with the Washington-based Republican Main Street Partnership, received more than 90 percent of its $845,000 in donations last year from labor groups, according to reports filed with the Federal Election Commission.

The group is led by former Ohio Representative Steve LaTourette, a Republican who had good relations with labor in Congress. He voted for a minimum wage increase, the 2009 auto bailout and a bill making it easier to organize a union.