The grandson of HB Reese, the inventor of Reese’s Peanut Butter Cups, has accused the chocolate giant Hershey of faking a pledge to investors to switch back the recipes of its popular products – including KitKat – to the original milk and dark chocolate ones.

A confectionary-focused dust-up between Brad Reese and the $42bn Pennsylvania-based company began in February when Reese, 70, accused the company of “quietly replacing” the ingredients – or “architecture” – in his grandfather’s invention with cheaper “compound coatings” and “peanut-butter-style crèmes”.

At a recent Hershey investor conference, the company said it would change about 3% of select products to the original recipes but maintained it had never altered the renowned Reese’s Peanut Butter Cups.

The company’s chief growth officer, Stacy Taffet, said Hershey was “transitioning our sweets portfolio to colors from natural sources, and ensuring that all Hershey’s and Reese’s offerings are consistent with their brand’s classic milk and dark chocolate recipes”. The changes are planned to come into effect by next year.

But Reese accused the company of “ingredient drift across flagship brands” and described the move “as a board level accountability problem” that caused shareholders to sell stock. “Your consumers are revolting,” he added.

Reese further told the New York Times he is not satisfied and the changes were not coming quickly enough. “This is just a PR stunt; there’s no victory here,” he said in an interview with outlet. “If they were serious, they would do it right away.”

The company has said the changes were already under way but not in response to Reese’s criticism, saying it had previously decided to revert to classic recipes after seeing a 25% increase in research and development to fund talent, technology and nutrition science.

The issue has become something of a crusade for Reese, who alleges Hershey changed sometime after buying the Reese’s brand in the 1960s.

In his original complaint to the company, issued on Valentine’s Day on the LinkedIn social media platform, Reese railed that recipes were “being rewritten, not by storytellers, but by formulation decisions that replace Milk Chocolate with compound coatings and Peanut Butter with peanut‑butter‑style crèmes”.

Reese said he’d noticed the difference in taste when he tried Reese’s Unwrapped Chocolate Peanut Butter Creme Mini Hearts.

“I opened it up, and I had about two of them, and I had to spit them out,” he said. “I dumped the entire contents into my kitchen garbage can, and I kept the pouch. I checked it and it wasn’t milk chocolate, it wasn’t real peanut butter.

“I’ve never in my entire life spit out a Reese’s product.”

But Reese’s family do not support his complaints. They said in a statement provided to USA Today by Hershey that “his statements and opinions are entirely his own and do not reflect the view or position of our family”.

“We continue to respect The Hershey Company, its leadership, and its longstanding role in our community,” they added. “We believe HB Reese would take great pride in the products produced under his name today and in the integrity with which the brand continues to be managed.”

Brad Reese didn’t accept that and accused the company of trying to “shoot the messenger”.

“Hershey can issue all the statements it wants,” he fumed on LinkedIn. “They changed the REESE’S product. They got caught. And now they’re trying to manage perception instead of fixing the problem. The evidence chain isn’t going away.”