Job vacancies have slumped by 12% this year, with areas such as financial services hardest hit, according to a new survey.
There was a 9% fall in April alone, with only hospitality showing a rise in job listings, said jobs site Indeed.
Employers' reluctance to recruit is being driven by uncertainty over the EU referendum and the introduction of the national living wage last month, said the report.
Mariano Mamertino, economist at the jobs site, said: "The introduction of the national living wage has already proved divisive, and our findings will fire the debate further. While thousands of the UK's lowest paid workers received a welcome boost to their April pay packet, the benefits have inevitably been concentrated in regions with higher numbers of poorly paid jobs, like North East England, Northern Ireland and Wales.
"Yet even by marginally eroding employers' appetite to hire more staff, the policy may have unwittingly made life somewhat harder for some jobseekers. Job vacancies in 12 of the 13 sectors tracked by Indeed fell in April, accelerating a trend that began in March following the announcement of the EU referendum.
"The combination of business uncertainty about the potential impact of a Brexit, the slowdown of the economy amid global economic headwinds and a sudden increase in the wage bill for many firms has triggered a sharp cooling in the jobs market."
A Government spokesman said: "The latest official figures show there are around 750,000 vacancies in the economy at any one time - 9,000 more than the same time last year - across a wide range of industries and roles.
"Meanwhile, the national living wage has given one million of the poorest paid workers a welcome boost to their earnings.
"We are building a more productive Britain and giving families the security of well-paid work."