Singleton was forced to resign from the city in February after a New York state audit accused him of numerous ethical violations in a former job. He did not respond to requests for comment for this article.

Robert Minor, who has been serving as the city's acting chief technology officer, referred questions to O'Doherty, citing a pending investigation by the city's inspector general. The mayor announced last week the hiring of a new chief technology officer.

O'Doherty said the equipment purchases last year were for a pilot program and made under an existing city contract for ongoing computer-related needs. He said the city spent only about $55,000 on phones and related equipment for the pilot program, and that other items were used for other purposes. All of the 124 switches have been installed in city offices, O'Doherty said.

Replacing the city's entire phone system would require a competitive bidding process, O'Doherty said, and all of the equipment for such an endeavor could not be bought under the existing "requirements" contract with Digicon Corp.

"There is no question that you cannot buy all the equipment that is needed under existing contracts," he said.

Still, O'Doherty said, the mayor has "a number of serious questions" about the IBM deal that Pratt is recommending.

"Is this the most effective use of our tax dollars?" O'Doherty said. "Has there been enough cooperation and collaboration between the comptroller's office and the technology office?"

O'Doherty questioned why only one company — IBM — was found to be the sole responsive bidder. "Was there enough competition for this?" said O'Doherty. "You would think there would be more qualified bidders instead of just one."

Pratt said she was "appalled" that the mayor's office would question the degree to which her staff collaborated with the mayor's team and called O'Doherty's questions "ridiculous." Her office and the technology office teamed up to assess the phone needs of all city agencies, she said. Moreover, the team that reviewed the bids included four employees who answer to the mayor and only one who answers to Pratt, the comptroller said.

Pratt pointed out that it was common for only one or two companies to submit a responsive bid for a city project. She dismissed the mayor's concerns as "just another angle to try to not approve this.

"The sooner the contract is approved, we can implement VoIP and start saving money," she said. "It is not an effective use of taxpayer dollars to delay the contract."

Pratt says she believes the Municipal Telephone Exchange, the office that oversees city phone operations and reports to her, is best poised to implement the new system. The comptroller's office has supervised the phones since the 1940s.

Moreover, Pratt questions why the technology office would attempt to take over the phone system when it helped her staff write the request for proposals and evaluate the bids.

"It seems like MOIT [the Mayor's Office of Information Technology] just wants to take over and implement its own system," Pratt said in an interview.

She said that Singleton told her that his proposal would cost the city about $2.2 million. But, said Pratt, when an independent consulting company, the Battles Group, reviewed the proposal, it determined that Singleton's plan was incomplete and would make it difficult to grow and maintain the phone system.

Singleton's plan includes detailed specifications of Cisco equipment that could be used to implement the phone system. The proposal also notes the importance of adding the Power over Ethernet, or PoE, switches to prepare for the phones. Such switches allow electricity to be run through a data cable and would be primarily used for VoIP phones in an office, but also webcams and security cameras.

Pratt said that when she issued a request for proposals in March 2011, three bids arrived: Aastra USA, IBM and Telephonet. The Aastra bid was disqualified because it arrived late, Pratt said. A panel of five city employees from various agencies reviewed the remaining bids and decided that Telephonet scored too low on certain technical specifications to be further considered.

Telephonet officials say they plan to protest any award of the contract to IBM. IBM officials, through an attorney, declined to comment for this article.

A Digicon spokesman declined to say why Digicon did not bid on the current contract or whether the company would consider bidding if the city rebid the contract.

The city's normally perfunctory Board of Estimates meeting took a dramatic turn last month, the first time the contract came up for a vote. Rawlings-Blake asked to defer the decision, which prompted angry words from Pratt.