Julie Mellor is to step down after six years as chairwoman of the Equal Opportunities Commission (EOC).
Mellor will become a partner at PricewaterhouseCoopers at the beginning of July.
Jenny Watson, deputy chair of the commission - who will take on Mellor's duties until after the general election - praised Mellor for putting the gender pay gap on the map.
"She has been a strong advocate of gender equality, particularly in promoting and supporting the changing role of fathers," Watson said.
Patricia Hewitt, secretary of state for trade and industry and minister for women, said: "The EOC has made great progress under Julie's leadership."
Watson will take over Mellor's duties until after the General Election.