State Rep. Martin J. Walsh, a candidate for mayor of Boston, called for the sale of City Hall Plaza to a private developer and the moving of City Hall to a new private development in the Downtown Crossing/Financial District/Government Center area.

"The 50-year-old Government Center Urban Renewal Plan is widely credited with the emergence of modern Boston," Walsh said in a statement. "While many discussions in recent years have concentrated on relocating City Hall, the opportunity exists to discuss a plan that instead drives economic growth. A 21st century economy has emerged, and the new mayor must refocus the development to the core economic engine of the city, the downtown. This area must evolve from a 9-5 weekday government-dependent culture, to a culture economically driven to add value 24/7 to surrounding businesses and neighborhoods."

The sale of City Hall Plaza is expected to generate $125 million to $150 million in one-time revenue, the Walsh campaign said. That 4.5 acre parcel would also be added to the tax rolls, generating an additional $10 million to $12 million annually, according to Walsh.

Walsh said he would engineer a "reverse RFP" to have a private developer bid to site, build, own and operate a privately financed City Hall based on a long term lease from city government on either a public or private site in or very near Government Center, Downtown Crossing or the Financial District.

Boston’s City Hall was built in 1967. A similar plan to sell City Hall and move it was promoted by Mayor Tom Menino in 2006. Menino’s plan called for City Hall to be relocated to the South Boston waterfront, but the plan did not gain much traction.