Investors should sell Snap shares due to significant negative sentiment from its core users over its latest app revision, according to one Wall Street firm.

MoffettNathanson, a boutique shop specializing in media and telecom, reiterated its sell rating on Snap shares, citing criticism of the social media company from its focus group surveys.

Snap shares fell 8.9 percent Monday.

"We hosted focus groups with three distinct cohorts – middle school students, high school students, and young college graduates," analyst Michael Nathanson wrote in a note to clients Monday. "Our first takeaway is that Snap's redesign has clearly been a bust. All three groups were uniformly disapproving of it … A year ago Snap was widely described as 'fun.' This year, the key word was 'annoying'!"

Nathanson reaffirmed his $10 price target for Snap shares, representing 37 percent downside to Thursday's close.

The analyst noted the focus groups disliked the new contacts page, Stories losing its own section and the increased frequency of alerts. He cited how the battery usage percentage for Snapchat declined 6 percentage points to 31 percent of all apps for middle school students versus a year ago.

"Betting on Snap's ability to monetize is a gamble we wouldn't want to take," Nathanson wrote.

Snap did not immediately respond to a request for comment.

Disclosure: CNBC parent NBCUniversal is an investor in Snap.



