The office run by the city’s new chief democracy officer botched its first assignment by sending out inaccurate letters warning 400,000 voters they might not be able to cast ballots in November because they’ve been placed in the “inactive” roll.

Some people who got the letters immediately took to Twitter to express bewilderment.

“Got a letter in the mail that says I’m currently listed as an inactive voter?” tweeted Nathan Holbert.

“I’ve voted in every election since living in NYC and checking online shows me registered and active. Why am I getting this confusing mail @NYCVotes? Either a BIG error or shady business.”

The city’s Board of Elections tweeted back that it wasn’t responsible for the screw-up.

“You ARE active and have never been in inactive status,” BOE said. “This letter was created by an outside entity not associated with @BOENYC. Not sure where they got their information from.”

The letters were sent Oct. 11 by the mayor’s new “Democracy NYC” office, headed by Ayirini Fonseca-Sabune, a recent $165,000-a-year-appointee.

Councilman Joseph Borelli (R-SI) called on the administration to turn over a list of the voters who were sent the letters.

He said he’s concerned what “matrix was used” and that it potentially targeted voters of a specific age, ethnicity, neighborhood or party affiliation.

“This is about voter suppression,” Borelli said. “An older person could read this letter and be confused and not go to the polls – that effects the elections.”

Eric Phillips, a de Blasio spokesman, defended the taxpayer-funded mass mailing by tweeting: “We mailed 400k(!) people that records show could be at risk of being ‘inactive’ on the rolls.

Because the BOE’s involved, no list is perfect. But we’re cutting a wide universe to ensure people check and fix it if they must. This is a good sign!”

Critics – including Democrats – weren’t buying Phillip’s line.

“Are you seriously throwing the BOE under the bus because your people screwed up?” tweeted Kim Moscaritolo, a Democratic district leader representing parts of Manhattan. “It’s not even about the list, it’s about the language of the letter.

“People in my district were freaking out thinking they’d been mistakenly removed from the rolls. This is unacceptable!”

Phillips insisted that only “a very small group of active voters may have received inaccurate letters …”

He claimed the mailing list used by vendor Civis Analytics originated from the BOE and that the city “is working to get to the bottom of why” it was used.

BOE did not return messages, but a source there said it had received “dozens of complaints” about the letters and that “nearly all of them where from registered voters who are active.”