The five-time presidential candidate wrote in a letter published by the paper that poverty wages and harmful conditions are "a consequence of tolerating outrageous stock buybacks."

"'Designed by Apple in California' has a nicer ring to it than 'assembled by workers paid about a dollar per hour, working 11-hour shifts, and sleeping eight to a room in the Jabil Circuit corporate dormitories in Wuxi, China,'" wrote Nader in the letter dated Oct. 23.

Apple is one of the top customers of contract electronics maker Jabil.

Apple declined to comment on Nader's letter, which echoes criticism from labor activists and right groups. Nader's critique comes as billionaire activist-investor Carl Icahn continues to urge the iPhone maker to buy back more shares using its $133 billion cash pile.

The iPhone maker has drawn fire in the past over practices at its manufacturing partners, most of which are based in China.

A rash of suicides in 2010 at Foxconn, Apple's main manufacturer, prompted widespread scrutiny in 2011 of working conditions across its supply chain.

The iPhone maker has since stepped up audits of its manufacturing partners and enlisted the services of the Washington-based Fair Labor Association. The organization has conducted regular reviews and reported on improvements in areas such as overtime and pay while saying more could be done.