Job vacancies in London’s finance industry fell 52 percent in December, the most in three years, according to a survey.

Recruitment firm Morgan McKinley attributed the drop partly to the holiday season and said its findings underscored the looming “Brexodus” from the City — particularly since there was also a 37 percent decline in job openings year-on-year.

“In December, the City is abuzz with holiday parties, not hiring, so a drop is to be expected,” Operations Director Hakan Enver said in the report, published Thursday. “But for it to be such a seismic drop is alarming.”

Morgan McKinley cited firms’ frustration at the lack of progress in carving out a Brexit divorce agreement and said that a lot of good news — such as an increase in the number of skilled-worker visas being issued — was being overlooked in the confusion. Goldman Sachs Group Inc., Deutsche Bank AG and Bank of America Corp. are all said to be moving operations away from London in favor of cities such as Frankfurt and Paris in case of a no-deal departure.

There was a 30 percent drop in the number of London professionals seeking new positions in December compared with a year earlier, dwarfing the decline in 2016, Morgan McKinley said. And those bankers that did move jobs last month saw a 14 percent average salary increase — among the smallest of 2017.

“Brexit clobbered the City’s workforce in 2017,” Enver said. “Anyone sticking it out into 2018 is in it for the long haul.”