Former U.S. Secretary of State Hillary Clinton speaks during the Clinton Global Initiative America meeting in Chicago, Illinois, June 14, 2013. REUTERS/John Gress (UNITED STATES - Tags: POLITICS BUSINESS) Former U.S. secretary of state Hillary Clinton (John Gress/Reuters)

The founder of Media Matters, a left-leaning media watchdog group, is joining the Republican National Committee's call for CNN and NBC to halt their plans to produce programming about former secretary of state Hillary Clinton, the organization announced Tuesday.

"Given that this project could coincide with a potential Clinton presidential campaign, the timing raises too many questions about fairness and conflicts of interest ahead of of the 2016 election," writes Media Matters founder David Brock in letters sent Tuesday to the heads of CNN and NBC.

NBC is planning to develop a miniseries about Clinton, a possible 2016 presidential candidate, while CNN plans to produce a documentary about her.

RNC Chairman Reince Priebus wrote the networks Monday threatening to exclude them from the Republican primary debate process unless they forego plans to produce the programming. Priebus said Tuesday that he doesn't expect the networks to comply with his request, and therefore plans to "cut them out."

Priebus also said he intends to push for a presidential nominating framework that would penalize Republican presidential candidates who participate in any debates hosted or sponsored by the two networks, should they not comply with his request not to produce the films about Clinton.