(Bloomberg) -- Activist investor Carl Icahn’s attempt to get Apple Inc. to return money to shareholders was criticized by the California Public Employees’ Retirement System, the largest U.S. public pension.

“We are uncomfortable with a raider coming into a company with a proposal to disgorge cash,” Anne Simpson, Calpers’ head of corporate governance, said in an interview yesterday. “Carl Icahn is a Johnny come lately.”

Calpers, with more than $270 billion in assets, owned 2.4 million Apple shares as of Sept. 30. The fund is asserting itself after Icahn said earlier this month that he would try to win shareholder approval for his plan to ask Apple to increase the size of its stock buyback program.

Simpson said Calpers agrees with Apple’s current cash- management strategy, which includes plans to return $100 billion to shareholders in the form of dividends and buybacks.

“We like what they’re doing. They have a significant program for returning money to shareholders,” Simpson said. “Carl Icahn is late to the party. This debate’s already been had. I’m not sure what Carl Icahn’s proposal adds.”

Icahn, who has become a billionaire by buying stakes in companies and then publicly pushing for changes to boost the stock, has been urging Apple since August to increase the size of its repurchase plan. Icahn disclosed in a filing this month that he owns 4.7 million Apple shares, or about 0.5 percent of the iPhone maker.

Simpson criticized Icahn for being outspoken about his buyback plan, including Twitter messages about a dinner he had with Apple Chief Executive Officer Tim Cook.

“Sending tweets from under the dinner table -- this is unseemly,” she said.

Icahn didn’t respond to a request for comment. Steve Dowling, a spokesman for Apple, also wasn’t available.