CNN suffered its worst ratings among primetime viewers in the most coveted demographic by advertisers — dealing a gut punch to embattled new boss Mark Thompson.

The cable channel, which touts itself as “the most trusted name in news,” drew just 83,000 viewers aged 25 to 54 during the week of May 13-19 from 8 to 11 p.m. — its lowest-rated week since 1991, according to Nielsen.

By contrast, Fox News garnered more than the twice the audience in the key demo, with 186,000 viewers, according to Nielsen. Left-leaning MSNBC was a distant second with 111,000, the data showed.

“Thompson better get his act together before he completely destroys CNN,” a top TV news producer told The Post.

“It seemslike he’s thrown in the towel regarding cable.”

CNN’s three-hour primetime block during the week features the network’s highest paid anchor, Anderson’s Cooper, with his show “AC360” at 8 p.m., along with “The Source with Kaitlan Collins” at 9 p.m. and “CNN NewsNight” with Abby Phillip at 10 p.m.

Its total viewership for the week was also paltry with 494,000, compared with 2 million for Fox News — which shares common ownership with News Corp, the publisher of The Post. MSNBC pulled in 1.1 million, according to Nielsen.

“CNN’s new name is Cancelled Network Now,” a media insider quipped.

“Young people are as interested in Anderson Cooper as they are in Liza Minnelli.”

A spokesperson for CNN told The Post the network’s primetime ratings are “all growing year over year” among viewers aged 25-54.

The rep added that the network’s primetime lineup, starting from “Erin Burnett Outfront” at 7 p.m. to its rebroadcast of “Anderson Cooper 360” at midnight, is “registering double-digit, year-over-year growth” in total viewers.

Thompson has been under the gun to turn around the sagging ratings and modernize the organization. – The former New York Times and BBC executivewho was hired last August by Warner Bros. Discovery CEO David Zaslav after the disastrous 13-month tenure of Chris Licht.

He has left the struggling primetime lineup in place, while revamping the equally problematic morning schedule.

“Zaslav went to a programmer in Licht. Now he went to a guy that doesn’t know how to program TV,” the producer said.

Last week, Thompson publicly laid out a plan centered on CNN’s verticals, which has been described by insiders as a revision of the plan launched by former CNN boss Jeff Zucker seven years ago, in which the network launched culture- and lifestyle-focused digital verticals and tiered subscription offerings built around network personalities.

We dont believe news is just politics, Thompson said during the company’s presentation to advertisers in New York.

Business and tech are news. Climate and weather are news. Health, wellness, and living longer are news. So expect to see us build new branded verticals in all these areas on TV, on our apps, and across our other platforms.

Another media insider said Wednesday: “I know it’s clich to say but Thompson is rearranging the deck chairs on The Titanic. He has no new ideas yet. But maybe his old media playbook will work. “

Last month, Thompson said the network faces an “existential crisis,” as it deals with cord cutting and the shrinking cable TV business.

There areplenty of things we have to fix at CNN, Thompson, said at the time.

He unfurled a five-point plan on March 1 that included vague bullet-point items: Building our digital future, A global integrated multimedia news operation, Future-proofing TV production, Developing new sources of revenue and Communication and culture.

It was immediately panned by industry experts.

Its a five-point plan to make five-point plans, a media exec told The Post at the time.

In other words, there is no plan, but we are really planning to make lots of plans. And rest assured, there are lots of people overseeing the planning to make plans. And Mark is overseeing all of the people planning to make plans. So dont worry. Weve got this totally under control!

Thompson’s lack of bold moves since taking the helm last October has led to much consternation among staffers, The Post previously reported.

He has made some internal leadership changes, including promoting Virginia Moseley —a hard-charging news executive who some staffers have called an ahole and a tyrant to lead the newsroom as executive editor.

Thompson also canceled “CNN This Morning,” which had been co-anchored by Phil Mattingly and CNN veteran Poppy Harlow, who departed the network after being offered a lower-ranking job.

The ill-fated morning show was the brainchild of Licht, who was ousted shortly after the network cut ties with controversial anchor Don Lemon.