Ahead of Apple Pay's expected launch in China later this week, new research suggests that growth is slowing in U.S. iPhone users' adoption of the mobile payment system.
"I think Apple Pay has been unfortunately a disaster," said Patriarch Equity CEO Eric Schiffer told CNBC on Wednesday. "There's very slow growth. It's helped to tank the stock, frankly."
In a recent survey, research firm First Annapolis found that 20 percent of iPhone 6 owners reported using Apple Pay at least once last December, down from 22 percent last spring. Among those who have adopted Apple Pay, 15 percent reported using it regularly compared with 19 percent last spring.
First Annapolis surveyed 580 iPhone owners to extrapolate its data on user adoption rates. It said that the margin of error for that subset of iPhone 6 users was plus or minus 3.3 percentage points, with a 95 percent confidence level.
Still, the results added evidence to the slowing growth of Apple Pay. A survey of 3,000 people by Phoenix Marketing published late last year found that after the payment system launched in 2014, it was adopted by 11 percent of cardholding households in February 2015. That figure increased to 13 percent of households in July, then to 14 percent by September, according to Phoenix.
"Like all new technology, consumers must adapt and change their habits," Electronic Transactions Association CEO Jason Oxman said in an email to CNBC. "In the case of mobile payments, they must change a 40-year habit of paying with a plastic card."
Apple said in its latest earnings report that Apple Pay transactions have seen double-digit monthly growth since its launch and that billions of dollars have been spent using the payment system.
To use Apple Pay, an iPhone 6 or iPhone 6S user can wave their phone over a vendor's contactless reader with a finger on the phone's Touch ID. Users can also use Apple Pay by accessing Apple Wallet with a double-click of the phone's home button while the phone is locked, or by finding and pulling up Apple Wallet on their phones.
Apple Pay, though, doesn't just compete with the likes of Google's Android Pay. Credit card companies themselves have rolled out so-called "contactless" payment systems.
MasterCard spokesman Brian Gendron said that contactless payments are 59 percent faster at checkout compared with dipping or swiping cards at vendor terminals. More than two-thirds of contactless payment users see it as equally or more secure than traditional forms of payment, Gendron said in an email.
Apple did not immediately respond to a request for comment.
DISCLOSURE: Neither Schiffer nor his fund own a position on Apple's stock.