Britain's low-paid labour market could be hit "hardest" if the country votes to leave the EU and new immigration rules are brought in, according to a study.
Hypothetical analysis carried out by the Migration Observatory at the University of Oxford reveals the potential impact on EU migrants and the main industries in which they are employed.
The observatory applied current non-EU visa restrictions to EU workers for the study, called the Potential Implications of Admission Criteria for EU Nationals Coming to the UK, and carried out for the Financial Times.
When determining eligibility for employment sponsorship, non-EU migrants must meet the skill levels required. To qualify for a Tier 2 visa an individual must have a job offer in a graduate-level position and be earning at least £20,800.
Findings showed that as many as 96% of EU workers on Britain's farms and up to 94% employed in hospitality and retail sectors would not meet this criteria.
Dr Carlos Vargas-Silva, the author of the report, said the biggest challenge with analysing the impact of Brexit on migration before the vote was that there were uncertainties about what policies EU migrant workers would face.
He added: "Most sectors of the UK labour market now have a significant EU migrant workforce - and many of these are lower paid sectors, such as hotels and manufacturing.
"Even if the immigration system is redesigned after a Brexit vote, any system that selects EU workers based on skills and pay is likely to hit these sectors hardest."
The retail, hotel and restaurants sector is currently the largest employer of workers born in EU countries.
With the public administration, education, health, banking and finance the second and third major employment sectors of EU nationals.
The report states: "If admission requirements were imposed on EU citizens following a vote to leave the EU, there is no reason to assume that migration policies would be the same as the ones that currently apply to non-EU nationals.
"Ending free movement would be a significant change to the UK immigration system, and it is likely that any move to impose admission requirements on EU nationals would be accompanied by a wholesale review of the immigration system overall."