The monthly Recruitment and Employment Confederation (REC) and KPMG Report on Jobs shows job vacancies continued to increase during July, but the latest improvement was the smallest increase for six months.
Average starting salaries for people placed in permanent jobs also increased "modestly" during July. Hourly rates of pay for temporary staff fell slightly.
By category, engineering/construction and medical staff were the most sought-after, with computing staff demand also outstripping most other categories.
Recruitment and Employment Confederation chief executive Kevin Green said: "Employers are still hiring and the number of vacancies has grown but fragile confidence means they are taking longer to make decisions about appointments and the whole process of recruiting is slowing down.
"On a positive note, there are some sectors that are defying this month's decline and continuing to experience significant demand for staff, most notably engineering, computing and healthcare."
Permanent staff in high demand in the computing sector were business analysts and specialists in digital marketing, infrastructure, .NET, PHP, and SAP, along with project managers and IT architects.
Data from the Office for National Statistics shows that overall job vacancies were up 2.6 percent on an annual basis in the three months to June. Internet-based recruitment spending rose by 4.6 percent in the first quarter of 2012, up from 0.8 percent in the final quarter of 2011, and the fastest growth for one-and-a-half years.