Twitter's stock could fall by up to 80 percent, a hedge fund manager has warned, arguing that the company is not backed by a "sound valuation."
Shares of microblogging website Twitter started trading at $45.10 when it floated on the New York Stock Exchange earlier this month. On Thursday, Twitter shares closed at $42.
But Pedro De Noronha, managing partner at Noster Capital hedge fund, said trading the company's stock was "for punters."
"I don't think there is any serious investor who's really looking at Twitter and thinking, 'I'm going to double my money,'" he said in a television with CNBC. "Maybe one day in the not too distant future we'll be able to buy it at 80 percent off the current level."
(Read more: Cashin: I'm worried about return to dot-com bubbles)
Noronha added that Twitter was not valued on "any fundamental metrics," and compared owning the stock to owning a Porsche.
"A Porsche 911 turbo adds value to you as an owner. But if you pay $2 million for it, it could come down to $100,000 and it still adds value to you - but at $2 million you would have been overpaying for it."
His comments come as the results of a CNBC survey (of 1,750 European executives) revealed that Twitter's reputation appears to be declining.
The latest wave of the survey, carried out in September by Tpoll, found a 61 percent drop in the number of executives who considered Twitter to be trustworthy between 2012 and 2013. Meanwhile, the number of those questioned who thought it was a respected brand slipped 40 percent over the same period.
Mark Ursell, Tpoll's CEO, said the drop could be due to increased social media choice or because companies had become more about "corporate advertising" than connecting with their users.
Twitter priced its shares as $26 dollars each when it held its initial public offering (IPO) on November 7. The share price saw a massive spike on the first day of trading, shooting up over 75 percent to top $46.
But George O'Connor, technology analyst at stockbroker Panmure Gordon, stressed that tech valuations were about blending "sentiment and fundamentals," adding that Twitter's valuation had to be taken in context.
"It is a huge landscape and like any landscape it has peaks and troughs. When you look at Twitter's fundamentals it looks very expensive. It is off the clock in relation to the broader technology companies. But in that broader tech space you have companies going into reverse," he told CNBC in a phone interview.
—By CNBC's Arjun Kharpal: Follow him on Twitter @ArjunKharpal