Growth in starting salaries also eased back to the slowest pace for four-and-a-half-years, it found.
The monthly KPMG and REC report on jobs showed a slight improvement in permanent job recruitment activity, which fell at the slowest rate since May, but remained in decline.
The influential report showed a reading of 44.2 for permanent placements in the UK last month, up from 40 in July.
However, any figure below 50 represents decline in the job market, with levels over 50 showing growth. The data therefore indicated another month of contraction.
The downturn in temporary billings also eased, with a reading of 46.8 in August up from 44.6 in July, though also still firmly in contraction.
But it showed the availability of staff increased at a “rapid and accelerated rate” in August, with upturns in permanent and temporary labour supply the most pronounced since November 2020.
Neil Carberry, chief executive of REC, said: “There is certainly potential out there, but with fewer vacancies and more candidates looking for work, the overall picture is still subdued.
“While we have seen a summer slowdown, we will hopefully see more positive signs when the September data come through next month.
“All eyes are now on the autumn Budget, in hope now that the Chancellor won’t do any further damage to the labour market with costs on hiring.”
The data comes after a survey by the Bank of England signalled last week that UK businesses cut jobs at the fastest pace for almost four years in August amid pressure from higher taxes and labour costs.
The Bank’s regulator survey of company finance chiefs shows UK firms cut employment by 0.5% over the three months to August.
It represents the biggest drop in employment levels since September 2021.
Firms have seen their wage costs soar after the Government hiked National Insurance contributions and the minimum wage in April.
Jon Holt, group chief executive and senior UK partner of KPMG, said that mixed business confidence and worries over the wider UK economic outlook was holding back hiring.
He added: “Given the speculation around upcoming Budget measures, it’s unlikely we’ll see a significant shift in recruitment patterns in the near term as businesses evaluate their investment strategies in response to policy commitments and the rapid pace of change brought by AI and new technologies.”
The KPMG and REC report surveyed around 400 UK recruitment and employment consultancies in the last two weeks of August.