Some Democratic National Committee (DNC) members and supporters of Sen. Bernie Sanders (I-Vt.) are venting frustration at DNC Chairman Tom Perez over his initial appointments to the committees that will oversee the rules and party platform at the nominating convention in Milwaukee later this year.

Sanders's allies are incensed by two names in particular: former Rep. Barney Frank (D-Mass.), who will co-chair the rules committee, and Hillary Clinton's former campaign chairman John Podesta, who will have a seat on that committee.

The Sanders campaign unsuccessfully sought to have Frank removed from the rules committee in 2016, describing him as an "aggressive attack surrogate for the Clinton campaign."

And Podesta, a longtime Washington political consultant and Clinton confidant, is viewed with contempt by some on the left. One of Podesta's hacked emails from 2016 showed him asking a Democratic strategist where to "stick the knife in" Sanders, who lost the nomination to Clinton that year after a divisive primary contest.

"There's a very small number of appointments of allies to Sen. Sanders," said Yasmine Taeb, a DNC member from Virginia who has not endorsed a candidate in 2020 but attended the 2016 convention as a delegate for Sanders.

"The appointments also include individuals that are outright hostile to Bernie Sanders and his supporters," she added. "It's not the message the DNC should be sending to the grassroots right now when we're all working aggressively to defeat the racist in the White House."

The Sanders campaign did not respond to a request for comment, but national co-chair Nina Turner blasted the appointments in an interview with progressive online news channel Status Coup, calling it "an embarrassment" and a "slap in the face."

"If the DNC believes it's going to get away in 2020 with what it did in 2016, it has another thing coming," Turner said.

Over the weekend, the DNC's executive committee voted to appoint 25 people each to the rules, platform and credentialing committees for the nominating convention.

The appointments are only a fraction of those who will end up serving on the committees. Most of the members will be allotted in proportion to the number of delegates the candidates win over the course of the primaries and caucuses.

There will be 187 people on each committee, and the winner's supporters should make up a majority.

The DNC does not consider past endorsements when determining the committee chairs or initial members.

Rather, DNC officials said they look for policy experts to help shape the platform or for experienced Democratic hands who know their way around party bylaws to assist in the rules and credentialing process.

And there are high-profile Sanders supporters appointed to the committees as well, including Larry Cohen, who founded the pro-Sanders outside group Our Revolution.

"Our rules require the DNC chair to make a small fraction of appointments to three standing committees for the convention, and these appointments reflect the rich diversity of our party," said DNC national press secretary Brandon Gassaway.

"The remaining appointments will be made based on each state's election results. 2016 presidential preference was not considered for this convention's appointments. We are grateful for these appointees' commitment to the party and look forward to an energized convention where we will nominate the next president of the United States," he added.

Still, there is frustration among some DNC members that the committee chairs and initial nominations rely too heavily on a pool of "at-large" delegates, rather than state-elected members who represent the party's activist base.

"The DNC is supposed to provide resources and a platform for state parties," said Michael Kapp, a DNC member from California who has not endorsed in the primary. "But if we are consistently being excluded from the table, how are state parties supposed to feel?"

DNC officials said state party members will make up a far greater share of the committees once delegates are allocated and each candidate's supporters take their spots alongside the appointed members.

Other critics said the initial list has too many corporate lobbyists, which is out of step with the grassroots base.

On Sunday, DNC members from California sent a letter to Perez asking that paid employees or consultants to the presidential campaigns be excluded from the rules committee.

And some DNC members complained that they were only alerted to the appointments late on Friday ahead of the executive committee's Saturday vote. Some members derisively referred to the appointments as the "midnight convention committee picks."

"The subject of transparency and notice has been broached in the past with Chairman Perez in open meetings of the full DNC," said Terry Tucker, a DNC member from Colorado and a Sanders supporter. "Lack of transparency and input from the members continues to be a source of irritation."

Jeri Shepherd, who is also a DNC member from Colorado and a Sanders supporter, worried that the process would "undermine unity" in the run-up to the convention.

"It will be difficult to have credible messaging to our grassroots base that the convention process will be fair and reflect the will of the voters," Shepherd said. "If the voters do not trust the process, that will serve to dampen turnout and will also hurt our down-ticket races."

The initial appointments have long been the prerogative of the chairman and the DNC's executive committee. DNC officials said the appointments were passed along to members at the same point in time as they always are.

Andrew Werthmann, a DNC member from Wisconsin who has not endorsed in 2020 but represented Sanders on the rules committee in 2016, said the appointments were a missed opportunity for the national party to seek input from the rank-and-file.

"We have to do things differently," Werthmann said. "This is one of those things where people were looking to the party to build trust and community and we just have to do a better job."

The frustrations underscore the tricky dynamics the DNC faces in overseeing a hotly contested primary and keeping different factions united before the July convention.

Most Democrats have been happy with the DNC's handling of the record number of candidates seeking the party's nomination, with more than two dozen running at one point.

Under Perez, the DNC has addressed power imbalances by weakening the influence of superdelegates, overseen a more robust debates schedule and been transparent in setting the criteria for who qualifies for the debates.

Perez and his team had nothing to do with the party's disastrous 2016 convention, which took place under the cloud of WikiLeaks releasing hacked DNC emails that showed political bias in favor of Clinton over Sanders.

But Clinton's recent return to the spotlight to bash Sanders and relitigate both her 2016 primary victory and general election loss has reignited tensions between establishment Democrats and grassroots liberals.

With Sanders rising in the polls, there are new fears among his supporters that the national party will stack the deck against him, particularly if there is a contested convention.

Bob Mulholland, a DNC member from California who is backing former Vice President Joe Biden, dismissed the concerns, however, and said Perez has proved that he can be trusted.

"There's a reason we elect a DNC chair. He's the CEO, so let him drive the car," Mulholland said. "Whoever the nominee is, he or she will be in charge of their own convention. My message to Democrats is to stop attacking each other and train your focus on Trump."