Graduates drove a 50,000 fall in numbers of EU nationals working in the UK in the wake of last year's Brexit vote, according to new analysis.
Office for National Statistics figures released earlier this month showed that the number of EU-born workers in the UK fell 50,000 to 2.3 million in the last three months of 2016, compared with the previous quarter.
Now the Resolution Foundation think tank has found that the biggest falls took place among graduates and those working in banking, the public sector and construction.
The think tank warned that firms needed to start planning now for the possibility of a fall in high-skilled overseas workers when Britain finally left the EU in 2019.
While quarterly falls in numbers of workers in particular sectors are not uncommon, the Foundation said that the figures appear to show that the EU workers' flight from the UK was being led by graduates, rather than by the low-skilled workers who form the focus of much Brexit debate.
The number of EU-national workers who left during the three month period included 45,000 from the mainly eastern European countries which entered the EU in 2004, as well as 30,000 from the longer-standing members in western Europe. Meanwhile, numbers of Bulgarian and Romanian workers rose by around 25,000.
The think tank's analysis showed that while there were falls across a range of sectors, including lower-paying hotels and restaurants, the biggest falls were in higher-paying finance posts and the public sector, along with construction.
The Foundation's economic analyst Stephen Clarke said: "Lower migration was one of the key issues during the EU referendum campaign, and it seems the vote has already had an effect, with the number of EU-born workers falling by 50,000 during the final three months of last year even without actual policy change.
"While it's too early to draw any firm conclusions about post-referendum migration levels, the initial reduction looks to have been driven by graduates, with some of the fastest falls being in finance and the public sector.
"This trend highlights that labour market adjustment to lower migration levels may not just be in the lower paid sectors that have dominated much of the debate.
"With the Prime Minister making control of migration a key priority for Brexit, firms should plan for the likelihood that the availability of migrant labour in Britain falls once the UK leaves the EU.
"That might mean a combination of investing in machinery, or rethinking their recruitment and training policies, all of which takes time, so employers need to start preparing now."