In a Friday letter to DNC Chairwoman Debbie Wasserman Schultz obtained by CNN, Sanders said the chairs of two convention committees are active supporters of his rival.
The two leaders -- Connecticut Gov. Dannel Malloy, co-chair of the Platform Committee, and former Massachusetts Rep. Barney Frank, the Rules Committee co-chair, are "aggressive attack surrogates" for Clinton. Frank has long battled with Sanders, penning an op-ed
in Politico last summer titled "Why progressives shouldn't support Bernie."
"I do not, and the millions who have supported our campaign will not, have any confidence that either of them will conduct committee proceeding in an even-handed manner," Sanders wrote in the letter.
Sanders, who has tussled with the DNC
several times this election season, said he's also disappointed that Wasserman Schultz selected only three of the more than 40 names he submitted for the standing committees.
"If the process is set up to produce an unfair, one-sided result, we are prepared to mobilize our delegates to force as many votes as necessary to amend the platform and rules on the floor of the convention," Sanders wrote.
Sanders also wants more of a say on the 15-person committee that drafts the party's platform. Noting that he's secured 45% of the pledged delegates awarded and expects to get more, he'd like each campaign to choose seven members, rather than four. The final member would be a chair jointly picked by the two campaigns.
The DNC says it is acting in an even-handed manner.
"Because the party's platform is a statement of our values, the DNC is committed to an open, inclusive and representative process," the committee said in a statement. "Both of our campaigns will be represented on the drafting committee, and just as we did in 2008 and 2012, the public will have opportunities to participate."
Friday's letter was released a week after the Sanders' campaign withdrew its lawsuit against the committee that claimed the party had unfairly blocked its access to a critical voter database in December.
The lawsuit came after a Sanders staffer exploited a software error to improperly access confidential voter information collected by Clinton's team. The DNC database is a goldmine of information about voters and being blocked from it threatened to complicate Sanders' outreach efforts just weeks before the Iowa caucuses.
The incident also fueled a long-held belief in the Sanders camp and among his allies that the DNC was stacking the deck in favor of Clinton.