State Lottery officials approved a proposal Tuesday to move their headquarters to Dorchester over the objections of union leaders and local officials in Braintree, who questioned whether uprooting the agency from its longtime home is worth the cost.

The unanimous vote by the Massachusetts State Lottery Commission came after a lengthy debate fueled largely by complaints from SEIU 888, which argued that the new 10-year, $15.2 million lease the board approved would dramatically hike costs and was negotiated with no union input.

The decision will move approximately 140 employees from Braintree to a 32,000-square-foot space in a Mount Vernon Street office building near Kosciuszko Circle.

Meanwhile, at least 160 other employees working in the lottery’s warehouse and regional office at the current Braintree location could ultimately stay, though those lease negotiations are ongoing.

Treasurer Deborah Goldberg, who chairs the commission and oversees the lottery, backed the move, arguing it puts the agency’s administrative offices within steps of the MBTA’s JFK/UMass Station on the Red Line. In Braintree, the closest station is 2½ miles away.

But officials acknowledged it also comes at a price. The lottery currently pays $2.2 million a year under its expiring lease for the 100,000 square feet covering the headquarters, warehouse, and regional office.

In Dorchester, the lottery will pay on average $1.5 million per year — plus whatever it negotiates under a new deal to cover the other two operations.

“The cost is significantly higher than the old lease,’’ said Michael R. Sweeney, the lottery’s executive director.

Goldberg’s office has asked the Legislature for a $1.6 million boost to its budget next fiscal year to cover relocating, though some of it is for one-time costs.

But state Representative Mark Cusack, a Braintree Democrat, said Goldberg’s office should show a justification for the move.

“It strikes me as largely unnecessary and not in the best interests of the operations of the lottery,’’ Cusack said. “Every level of government is looking at efficiencies and consolidation, and this is going the other way.’’

Mayor Joseph C. Sullivan of Braintree, a former lottery director, said he has questions about how the move will affect the lottery’s bottom line and the revenue that goes back to cities and towns.

“This is the treasurer’s prerogative,’’ he said. “The decision has been made, and we will adjust to the reality of that decision.’’

Sweeney argued that the lease price probably would have risen anyway if the lottery headquarters had stayed in Braintree.

He also said that putting the headquarters lease out to bid was driven in part by requirements laid out by another state agency, the Division of Capital Asset Management and Maintenance, which helped negotiate the lease with the new landlord, Bayside Merchandise SPE LLC.

It was the lottery, however, that “made the decision for DCAMM’’ to pursue different leases for the three different operations in Braintree, according to a memo division officials wrote to Sweeney.

“The lottery has been in the [Braintree] building for 20 years without a legal bid put on the street to test the marketplace,’’ Sweeney said at the meeting. “That is not good business on behalf of the Commonwealth.’’

Sweeney and Goldberg acknowledged not communicating with union officials earlier in the process, though the director argued it was difficult to raise the effect of relocating with the union before a lease was finalized.

Goldberg called it a “lesson learned’’ for any upcoming lease negotiations for other lottery properties.

“I am a huge supporter of the union, 888, and all unions,’’ Goldberg said during the meeting. “We will be working with you.’’

It did little to appease union officials.

“The issues we were talking about [in the meeting] — transparency and inclusiveness — this administration hasn’t been transparent,’’ Tom McKeever, the secretary treasurer of SEIU 888, told The Boston Globe after the meeting.

“We are absolutely blindsided. We found out about this vote through the Mass. State Lottery website,’’ he said. “Members just can’t wrap their head around it. It doesn’t make sense in a cost-effective way.’’

The potential move to Mount Vernon Street, first floated publicly by Goldberg in February 2017, has its own political backstory.

It includes last year’s debate over the governance of the state’s new legal marijuana market, which, under the ballot question passed by voters in 2016, was entrusted to Goldberg’s office.

But lawmakers largely sidelined Goldberg in their legal rewrite, passing a bill that created a five-member commission to oversee the industry that includes just one direct appointee from the treasurer’s office.

Leading the House negotiations was Cusack.

He has denied that the decision to strip the treasurer’s office of much of its marijuana powers was spurred by the lottery’s potential move, and Goldberg, too, argued Tuesday that politics played no role in the relocation.

Matt Stout can be reached at matt.stout@globe.com. Follow him on Twitter @mattpstout.