MADISON, Wis (Reuters) - Wisconsin Governor Scott Walker's chief of staff Keith Gilkes, who helped steer the Republican governor's controversial push to curb collective bargaining rights of public sector workers, resigned on Friday.

Walker's office said that Gilkes would leave his post next week to return to his consulting business and begin advising the governor ahead of a possible recall effort against him next year.

Gilkes, who led Walker's 2010 campaign, is the second top aide to the Republican to step down in as many months. He will be replaced by Deputy Chief of Staff Eric Schutt.

The fight over that anti-union measure thrust Wisconsin into the national spotlight, igniting massive pro-union protests and political fights that led to a record nine recall elections this summer.

Democrats and union leaders have vowed to force Walker to defend himself in a recall vote sometime next year.

Gilkes said he would take on other clients when he returns to the Champion Group, but will not engage in any lobbying. His last day on the state payroll will be October 8.

"Keith did an outstanding job helping to craft and implement our ambitious pro-jobs agenda," Walker said. "I would like to thank him for his dedication to public service, and acknowledge the tremendous amount of time and energy he spent working to help improve state government."

(Reporting by Jeff Mayers in Madison; writing by James B. Kelleher in Chicago; Editing by Cynthia Johnston)