American political activist the Rev. Jesse Jackson on Wednesday launched a new campaign aimed at drawing awareness to the lack of racial diversity in the executive ranks of top-tier Silicon Valley firms, including Apple.

"Technology is supposed to be about inclusion, but sadly, patterns of exclusion remains the order of the day," Jackson wrote in a letter issued under the Rainbow PUSH Coalition banner. "When it comes to African Americans on Board - ZERO. C-suites, ZERO. Minority firms in IPO's and financial transactions, advertising and professional services - ZERO. These ZEROES are contrary to the enlightened values exposed by the industry. Rainbow PUSH is seeking meetings with tech leaders to address these ZEROES head on."

In addition to Apple, the coalition distributed copies of the letter to Twitter, Facebook, Hewlett Packard, Google and "other iconic Silicon Valley technology companies." It is not the first time Apple has come under fire for the relative lack of diversity in its executive ranks, which features few women or minorities.

Former Avon CEO Andrea Jung is the lone female member of the company's board, while communications vice president Katie Cotton and human resources head Denise Young-Smith — an African-American — are the only women known to report directly to CEO Tim Cook. Incoming retail chief Angela Ahrendts, now the CEO of fashion house Burberry, will be the first woman on Apple's senior leadership team when she joins later this spring.

In January, following pressure from shareholders, Apple directors altered the charter of the Nominating and Corporate Governance committee to include language codifying a commitment to diversifying the makeup of the board.