A cache of more than 19,000 emails from Democratic party officials, leaked in advance of Hillary Clinton’s nomination in Philadelphia, details the acrimonious split between the Democratic National Committee (DNC) and Clinton’s former rival, Senator Bernie Sanders.

Several emails posted by Wikileaks show DNC officials scoffing at Sanders and his supporters, and in one instance questioning his commitment to his Jewish religion. Some emails show DNC and White House officials mulling whether to invite guests with controversial backgrounds to Democratic party events.

Earlier this year, Russian hackers stole material from the DNC’s email system, the party and an investigating cybersecurity firm acknowledged last month. Wikileaks did not reveal how it acquired the files, though a hacker who goes by “Guccifer 2.0” has also claimed to have breached the party’s system.

President Vladimir Putin has claimed Russia does not meddle in other countries’ domestic affairs, saying that he would be willing to work with either Clinton or the Republican nominee, Donald Trump. But a Russian hack would fit a past pattern of attempts on government servers, and a member of Putin’s ruling party recently expressed a preference for Trump, whose campaign chairman formerly advised a Ukrainian president ousted for his pro-Putin stance.

Last month Debbie Wasserman Schultz, the DNC’s chairwoman, said the breach was a “serious incident” and a private contractor hired to sweep the organization’s network had “moved as quickly as possible to kick out the intruders and secure our network”.

On its web page, Wikileaks said the new cache of emails came from the accounts of “seven key figures in the DNC” and warned that the release was “part one of our new Hillary Leaks series”.

Among the officials whose emails were made public were the DNC spokesman Luis Miranda, the national finance director, Jordan Kaplan, and the finance chief of staff, Scott Comer. Other DNC and media figures and even some White House officials communicated with them between January 2015 and last May, Wikileaks said.

The emails include several stinging denunciations of Sanders and his organization before and after the DNC briefly shut off his campaign’s access to the party’s key list of likely Democratic voters.

The DNC temporarily curtailed Sanders’ access to the list in December 2015, after the party accused his campaign of illegally tapping into confidential voter information compiled by the Clinton campaign. The Sanders campaign briefly sued the DNC but the parties reached an accord, and the suit was dropped in April.

The emails show that after the furor over the voter records was resolved, hostility simmered from top DNC officials over the Sanders campaign.

In mid-May emails with Miranda, his deputy, Mark Paustenbach, questioned whether the DNC should use the spat to raise doubts about the Sanders campaign.

“Wondering if there’s a good Bernie narrative for a story, which is that Bernie never had his act together, that his campaign was a mess,” Paustenbach wrote.

Miranda spurned the idea, although he agreed with Paustenbach’s take: “True, but the Chair has been advised not to engage. So we’ll have to leave it alone.”

The same month, in another email to DNC officials, another official identified only as “Marshall” said of Sanders: “Does he believe in a God. He had skated on saying he has a Jewish heritage. I think I read he is an atheist. This could make several points difference with my peeps.”

The Associated Press emailed Miranda, Paustenbach and the DNC chief financial officer, Brad Marshall, about the Wikileaks releases but they were not immediately available for comment. Sanders campaign officials were also not immediately available.

The Wikileaks releases also included exchanges between DNC officials and White House event planning officials about whether to allow several influential Democratic party donors to attend events where Barack and Michelle Obama were scheduled to appear. The emails contained lengthy discussions about the donors’ backgrounds, including, in some cases, criminal histories.

One email exchange concerned the singer Ariana Grande, who was considered to perform at a DNC event but was caught in an infamous online video that showed her licking other customers’ doughnuts at a bakery in California. DNC officials also worried about a comment in the same video: “I hate America.” Grande, whose real name is Ariana Butera, later apologized for the comment.

According to the emails, White House officials vetoed Grande’s performance.

In June, Trump accused the DNC itself of masterminding the hack, which had accessed the party’s “opposition file” of research into the conservative candidate.