Employers are having to increase pay for skilled workers because fewer people are looking for jobs, according to a study.
Research by the Recruitment and Employment Confederation (REC) found placements into permanent jobs continued to increase "sharply" last month.
Starting salaries increased at the fastest pace for 19 months, while the number of candidates for full-time and temporary jobs fell.
Recruitment agencies said there was a particular increase in demand for engineers, accountants and for temporary jobs in nursing, hotel and catering.
Tom Hadley, REC's director of policy said: " With fewer people currently looking for jobs, employers are having to increase starting salaries to secure the talent they need.
"This is creating great opportunities for people with in-demand skills who are prepared to change jobs, but it's also putting unsustainable pressure on many businesses.
"Existing skills shortages are being exacerbated by Brexit.
"For example, demand for accountants and other financial roles has increased recently as organisations try to protect themselves against economic uncertainty.
"London alone employs almost 200,000 EU nationals in these roles.
"Policies which make it more difficult to recruit and retain these people will put business growth at risk."