The recruiter says R&D and procurement positions are being relocated to Eastern Europe as auto businesses seek to create low-cost hubs for innovation, with senior supply chain positions also being reviewed.
Jobs are switching to Romania, Hungary and Bulgaria in particular, it added.
The news comes after Japan's ministry of foreign affairs delivered a memo to the UK government raising concerns over the impact of Brexit for carmakers, including the potential for manufacturers to pay tariffs in both the EU and the UK.
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Renault, Daimler, Audi and Jaguar are among the firms to have either announced new bases in Eastern Europe, or have already established sites.
DHR managing partner Frank Smeekes said: “For some industry players, the UK now makes less sense as a long-term base for their high level European operations, if they can make the knowledge/cost ratio stack up elsewhere.”
“While this is not going to be an overnight transformation, this trend looks set to grow among both manufacturers and suppliers over the next two years or so as they seek to maximise intellectual capital and consolidate their operations into fewer key locations, while containing their costs.”
And while salaries remain roughly 40 per cent lower, senior executive based in the UK could be tempted by relocating to markets ike Bulgaria, were rents are 86 per cent lower than London.
Smeekes said: “Automotive companies will have to invest time and resources into sourcing, attracting and retaining suitable candidates. If existing staff are unwilling to relocate away from the UK, competition for local or more mobile talent could heat up.”