The gag order came to light as boosters of Boston's bid to host the 2024 Summer Games revealed new details of their vision, and opponents concerned about the public cost worked to organise a referendum to block it.
"Mayor (Martin) Walsh is not looking to limit the free speech of his employees," said Laura Oggeri, a spokeswoman for Walsh, referring to a contract Walsh signed with the U.S. Olympic Committee in December banning city employees from criticizing the Olympics or the Olympic committees.
"This was standard boilerplate language... that all applicant cities have historically signed," she said.
The Boston Globe first reported on the contract earlier on Wednesday after obtaining it through a Freedom of Information Act request.
The U.S. Olympic Committee picked Boston earlier this month as the nation's candidate to bid for the Games, choosing the city over Los Angeles, San Francisco and Washington, D.C.
If it beats out rivals expected to include Doha, Qatar, Rome, and either Berlin or Hamburg in Germany, Boston would be the first U.S. Olympic host since Salt Lake City in 2002.
Boosters on Wednesday unveiled artist renderings of a temporary Olympic Stadium to be built in Boston's centre, and promised the event would be hosted at no public expense while creating long-term jobs.
Boston 2024 President Dan O'Connell said he expects operating the Olympics would cost $4.7 billion (3.1 billion pounds), all of which would be funded through broadcast revenues, corporate sponsorships, and ticket sales. He said infrastructure upgrades would be publicly funded, but are already needed.
Chris Dempsey, the co-chair of No Boston Olympics, said his group was concerned by a lack of public input into the process, and was exploring ballot initiatives, including a referendum, to block it. He said the public employee gag order could have a "chilling effect" as the city starts its public meeting process.
Walsh is planning public meetings to garner feedback on the plan. He has said he does not believe a referendum is needed, though his office has said he would not seek block one if it was organised.
A poll released on Tuesday showed three-quarters of Boston-area residents believe they should be able to vote on the issue, though more than half said they support the idea.
The deadline for cities to submit applications is Jan. 8, 2016. The International Olympic Committee will choose the winner at its 130th session in Lima, Peru, in 2017.
(Writing by Richard Valdmanis; Editing by Alan Crosby)
