Animal rights activists last week claimed another victory against beleaguered animal testing group Huntingdon Life Sciences, after the company's planned New York listing was pulled at the last moment.
The New York exchange would give no explanation for its decision, which was announced as Huntingdon chief executive Brian Cass was standing on the trading floor.
However it is understood that there were fears that the security of the exchange could be threatened by the animal rights activists.
Greg Avery, of activist group Stop Huntingdon Animal Cruelty (SHAC), said that the decision was "yet another slap in the face for HLS".
An activist group called Win Animal Rights (WAR) in the US had sent out an e-mail alert to 10,000 people saying that the exchange was now "a primary focal point for this campaign".
It is only four weeks since the company and the NYSE announced jointly that Huntingdon had been accepted on to the exchange.
The company originally left the NYSE and the London Stock Exchange, its main listing, over four years ago after a sustained campaign by activists.
Days later it emerged that one of the key animal rights protesters who campaigned against Huntingdon Life Science's US listing has a previous conviction for ill-treating animals.
Camille Hankins, 52, was fined $200 in 1995 after Peta, a US animal charity, seized 80 dogs and cats from her home.
Ms Hankins, of Brooklyn, New York, started an animal rights group called Win Animal Rights (WAR). She sent 10,000 emails on the morning of Huntingdon Life Science's prospective listing on the New York Stock Exchange, saying that the listing made the NYSE a "primary focal point of their campaign".
The exchange has still not commented on its decision, but it has been widely assumed that security implications of activism were the reason for the postponement. HLS remains listed on the Nasdaq over-the-counter bulletin board as Life Sciences Research.