Vacancies for professional workers such as accountants, lawyers and bankers have fallen for the third month in a row.
A study by the Association of Professional Staffing Companies showed a 7% fall in May, leaving demand 21% lower than a year ago.
Temporary vacancies for engineers defied the downturn affecting other professional jobs, rising by 6% compared with a year ago.
Ann Swain, the association's chief executive, said: "Fears that the resurgence in the jobs market seen at the start of the year might be short-lived appear to have been well founded. Once again, negative economic data and uncertainty over the eurozone has pushed employers back into wait-and-see mode.
"As always during a period of slow growth, there are bright spots amongst the gloom and some skills remain in strong demand. Engineering skills are faring much better in the jobs market, with vacancies for some roles up quite significantly.
"The economy has barely moved over the past 18 months which, combined with the on-off nature of the eurozone crisis, makes it very difficult for employers to commit to hiring decisions.
"Demand for temporary workers has proven more resilient than demand for permanent candidates, but vacancies are still down on this time last year."
