HARTFORD — The Hartford plans to relocate 700 workers from its Simsbury offices to its headquarters on Hartford’s Asylum Hill in a deal that has been in the works for months.

The Hartford Financial Services Group made the announcement Wednesday. It also confirmed plans to spend at least $140 million in renovations, already underway, to existing space at its Hartford campus — room enough to absorb the 700 workers, the insurer said.

The city council on Monday will consider phasing in tax increases over seven years that would result from the renovations. The renovations would push up property values and assessments by the city.

City leaders praised the influx of 700 workers and the renovations. The news comes just weeks after accounting firm CohnReznick announced that it will move nearly 200 workers to downtown Hartford by the end of the year.

“The Hartford’s decision to invest in its Hartford campus is a strong signal of their belief in the viability and opportunity that exists in our city,” Mayor Pedro E. Segarra said Wednesday.

Segarra said the renovations “can help recruit and retain more young talent.”

Hartford business groups say that The Hartford has a record of investing in its campus, including the establishment of a data center in 2010. That same year, it donated $2 million to buy and knock down the Capitol West building, an eyesore at the edge of its Hartford campus.

Even though The Hartford’s headquarters is outside of downtown, the insurer has been supportive of efforts to revitalize downtown, said Michael Zaleski, executive director of the Hartford Business Improvement District.

Recently, for example, The Hartford has been working with the district to launch a shuttle that would carry its employees from Asylum Hill into downtown during the lunch hour, Zaleski said.

“Any time there is an improvement at The Hartford or any other company, it’s always positive,” Zaleski said. “It benefits restaurants, retail and other amenities the city has to offer.”

In addition, more workers at the insurer’s headquarters could enlarge the pool of possible tenants for apartments that are under construction downtown, Zaleski said.

In January, Segarra hinted of more employees coming into Hartford. He told those gathered at the monthly “Rising Star” breakfast that a company would be moving hundreds of workers to the city in 2014. The name did not emerge publicly until Wednesday afternoon.

The Hartford is closing its massive Simsbury campus and marketing it for sale, a decision that it first announced in February 2013. At that time, The Hartford said that workers would be consolidated to Hartford and Windsor. The Hartford wouldn’t say how many employees it had in Simsbury or how the workers would be divided up.

The 133-acre Simsbury property on Hopmeadow Street includes a four-story, 641,000-square-foot structure. The town is working with The Hartford on options for the site. The Hartford is Simsbury’s largest taxpayer, contributing $1.6 million annually.

The Hartford wouldn’t discuss the scope or a time frame for its renovations. But in a letter to the city council from Segarra accompanying the tax-abatement proposal, the mayor said that the work would include improvements to heating and cooling systems, lighting and plumbing, a new roof and improvements to a parking garage.

“Many of the improvements are designed to increase energy efficiency and thereby, reduce operating costs,” the letter states.

The company has declined to say how many workers it has in Connecticut. The most recent figures available are from February 2013. At that time, its Connecticut workforce had fallen by 40 percent to 7,700 from about 13,000 five years earlier.

The company’s workforce has declined steadily since the end of 2008. It laid off employees and sold off major segments to focus on property-casualty. According to figures made available earlier this year, the company’s total employee count declined from about 31,000 as of Dec. 31, 2008, to 18,800 at the end of last year