Equity Residential’s The Alcott apartment tower, right, is seen rising next to The Hub on Causeway in January 2021. iStock photo / File

The anchor tenant of the Hub on Causeway is offering the bulk of its remaining office space for sublease amid a continuing surge of givebacks in Boston towers.

Verizon recently listed 190,000 square feet for sublease, a year after Google’s life science arm Verily subleased 109,000 square feet from Verizon on the 23rd through 26th floors.

The latest listing offers the 19th through 22nd floors and 27th through 29th floors for sublease. The Boston Business Journal first reported the latest downsizing by Verizon, which did not respond to a request for comment.

The city of Boston’s office market now has a record 3.8 million square feet of sublease availabilities, and direct vacancies of 19.1 percent, according to a JLL report released Thursday. The report cited permanent hybrid work arrangements for companies’ downsizing of real estate footprints.

Office sublease activity also is surging in the suburbs, with 500,000 square feet of activity in the first alone. Throughout Greater Boston, the sublease market is approaching 7.5 million square feet, according to JLL.

In 2018, Verizon leased 439,000 square feet as anchor tenant of Boston Properties’ speculative office tower at The Hub on Causeway, which was completed in 2021. The telecom giant leased the 15th through 31st floors of the office tower, while online security company Rapid7 leased the lower podium section. The front offices of the Boston Celtics and Boston Bruins leased an additional three floors in early 2020.