Scott Fortner said the franchise’s only intention in allowing the reality star to wear the outfit at the prestigious New York fashion event had been “publicity” and that more should have been done to protect the “cultural icon”.
It comes after photos posted online by Mr Fortner appeared to show damage to the gown, which has since been returned to Ripley’s following the event.
The images have caused backlash against Kardashian online, with social media users blaming her for the gown’s condition.
But Mr Fortner told the PA agency he had not intended for the outrage to be directed at the reality star.
“I think the disappointment that I’m experiencing is Ripley has made multiple statements that they were doing everything that they could to protect and preserve the gown,” he said.
“I do feel that it (was) irresponsible, this is not just a dress.
“This is a cultural icon. It’s a political icon. It’s a Hollywood icon.
“It’s part of American history from an event that happened 60 years ago and…it should have been archived and preserved and taken care of.”
He added: “I think a lot of people are really kind of coming down really hard on Kim Kardashian and that’s not my attempt here.
“It’s the most famous dress in the world.”
The gown, worn by Monroe during her famous 1962 performance of Happy Birthday to US president John F Kennedy, is the most expensive dress ever sold at auction, having gone under the hammer for 4.8 million dollars (£4 million).
“Who wouldn’t want to wear the dress if they were given an opportunity to do so?” Mr Fortner asked.
The historian, who has curated his own private collection of Monroe artifacts, said the gown was now “irreparable” as it was no longer possible to purchase the fabric it was made from.
Following the Met Gala, Kardashian shared a picture of the skin-tight gown, which was adorned with more than 6,000 crystals and hand-sewn by costumier Jean Louis.
Speaking about Ripley’s decision to loan it out to Kardashian, he said: “it’s unclear to me what the motivation was other than publicity.
“Because the amount of publicity that’s come from this has been really priceless, you couldn’t pay for the amount of publicity they’d have gotten and that’s really the only thing that I can think of as a reason for them to do it.”
Kardashian said she had been “so honoured” to wear the dress to the Met Gala and revealed she had lost 16 pounds in order to fit into it.