Central banks were forced to largely go it alone in the effort to save the world from economic ruin less than a decade ago, but it left monetary policymakers wielding too much power and vulnerable to a backlash that could undermine their independence, according to a former central banker who helped shape the global response to the financial crisis.

Paul Tucker, who served as deputy governor of the Bank of England from March 2009 to October 2013, spoke with MarketWatch about his new book, Unelected Power: The Quest for Legitimacy in Central Banking and the Regulatory State, which examines the weighty question of the role central bankers and other unelected experts should play in modern democracies.