Vacancies for engineers and computing staff have fallen by 6% in the past year, according to research.
The reduction is in contrast with financial services and marketing, where vacancies have increased by 3% and 14% respectively, said the Association of Professional Staffing Companies (APSCo).
Posts in the financial services sector increased by 3%, the study found.
Ann Swain, chief executive of APSCo, said: "The uncertain nature and timing of Brexit is now beginning to take its toll as we approach 2017.
"According to a recent survey of more than 1,000 firms by the Centre for Economic and Business Research, companies have abandoned plans for £65 billion of investment since the Brexit vote.
"This type of fall in confidence will, of course, impact hiring intentions."