The FBI is investigating the threat left for William Higgins, chairman of the NYSE Equity Members Association, in a voicemail message last week. In a brief but angry tirade, the man, whom the FBI believe is an NSYE member, implied that Mr Higgins’s car could be booby-trapped if he did not end his campaign against the merger.

The message was received at the offices of Grant & Eisenhofer, Mr Higgins’s lawyers. A transcript reads: “Mr Eisenhofer, you’d better tell Mr Higgins . . . if this deal doesn’t go through, he better have somebody start his car . . . because he is out of his mind. We were sucking wind with no bids for the seats and . . . no money for the leases . . . Now we got money and he wants more?” The man is said to have a well-educated American accent, is thought to be middle-aged and white. Such threats are a federal crime and carry a prison term.

Mr Higgins, who is pursuing legal action against the NYSE in relation to the proposed merger, said that he would persist with his campaign, believing that the draft merger undervalues the NYSE. “We have had to buy a remote starter for the car and have been told to park it away from the house. But I remain resolute in my cause and will not be bowed,” he said.

FBI agents from New Jersey, where Mr Higgins lives, are investigating the threat along with detectives from the New York City Police Department and Jim Esposito, NYSE head of security.

One man in North Carolina was believed to be helping the FBI with their inquiries but has been ruled out as a suspect.

The investigators said that the caller showed a detailed knowledge of the leasing and selling system that governs ownership of an NYSE seat.

Under the terms of the NYSE merger proposal, the 1,366 seat holders of the exchange, its effective owners, will each receive $300,000 in cash and a quantity of shares estimated to be worth about $3.2 million.

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