Hartford -- Gov-elect Dan Malloy tapped a key aide from his tenure as mayor of Stamford to be the state’s new budget chief Wednesday.

Ben Barnes, 42, served under Malloy for eight years, ending as director of operations for the city, a post Malloy said was the municipal equivalent to the job he will now assume: Secretary of the Office of Policy & Management.

Malloy announced the appointment at a crowded news conference in the Legislative Office Building, putting in a place one of the most important pieces of an incoming Democratic team that will try to close a $3.5 billion budget deficit while preventing, as Malloy has pledged, further damage to the safety net of programs helping the poor, the needy, local government and the middle class.

The challenge for Barnes, who Malloy hired away from the Connecticut Conference of Municipalities, will be daunting, the incoming governor said.

“I explained to him that he will get a day off in August, and not before,” Malloy said.

Barnes said he was “terribly honored” to join the administration, and eager to help Malloy and running mate Nancy Wyman “fulfill many of their campaign promises.”

A chief promise that is now squarely in Barnes’ lap is Malloy’s determination to move the state into full compliance with generally accepted accounting principles (GAAP), bookkeeping rules that adherents believe will cut down on the ability of legislators and governors to employ gimmicks and dissembling in balancing the state budget.

Barnes also expressed confidence that the new administration would succeed in making government operate more efficiently.

“He is a relentless streamliner,” Barnes said of his former and now current boss.

In Stamford, “we found many, many ways to maintain services while reducing the level of our expenditures.”

Malloy had a handy rejoinder when he was asked about the qualifications Barnes does not bring to the job, namely an absence of experience in the legislature, like that of his predecessor under Rell, the well-liked former state Sen. Robert Genuario.

When a reporter asked about whether Barnes knew how the Capitol and its processes worked, Malloy smiled.

“He knows how I work,” Malloy said.

Barnes has experience at the Capitol. A biography prepared by the Malloy administration’s transition staff notes that he worked as government finance director for CCM, the lobbying organization for local governments. He also worked as a planner in Hartford and in St. Petersburg, Fla., where Barnes’ father, Andrew, was the longtime publisher of the St. Petersburg Times.

Barnes has a Master’s degree in urban planning from New York University, and a bachelor’s degree in history from Swarthmore College in Pennsylvania.

Barnes currently serves as operating officer for the Bridgeport public school system. He lives in Stratford with his wife, Tania, and three sons.

More transition announcements are expected from Malloy, as he and a team of advisers, led by Wyman and chief of staff-designee Timothy Bannon, continue to vet candidates for state positions.

“One or two” more appointees could be named before Thanksgiving, Malloy said, but the majority will likely be announced after the holiday.

Malloy takes office Jan. 5, and must present a budget to the legislature in early February.