Businesses are unlikely to face a sharp drop in the number of eastern European workers in the UK following Brexit, according to a new report.
Migration Watch UK said its analysis suggests there is little need for continued immigration from the region to maintain the present number available for employment.
The campaign group's paper noted that concerns have been expressed that post-Brexit controls on the entry of EU workers will lead to serious shortages of labour.
But the study said labour force survey data indicates they are a "stable" population.
The stock of migrants from 10 eastern European countries - Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Slovakia, Slovenia, Romania and Bulgaria - appears to be increasing rather than decreasing, according to the report.
It said: "On the assumption that EU citizens who are here before the UK leaves the European Union will have their rights preserved, this analysis suggests that there will not be a need for any significant continuing inflow to sustain the existing east European workforce as it appears that previous arrivals have not in fact tended to leave the UK such as to need continual replenishment."
Migration Watch has called for restrictions on lower-skilled migration, saying curbs could reduce net migration from the EU by around 100,000 a year.
International net migration from Europe and the rest of the world has been running at near-record levels of around a third of a million, well above the government's target of less than 100,000.
The organisation's vice chairman Alp Mehmet said: "Employers will not face a cliff edge over their workers from the EU.
"In the past 10 years, very many migrants from Eastern Europe in low-skilled work seem to have stayed on so there is no sign that continued large inflows are needed to maintain the present number available for work.
"Cutting out this aspect of migration in future should reduce net migration by about 100,000 a year. This would be a major step forward in the government's efforts to reduce immigration."
Analysts have predicted that sectors such as construction, hospitality, social care and fruit picking are likely to be the main targets of any post-Brexit policies to reduce migration from the EU for work-purposes.
The Government is expected to seek to introduce controls on free movement rules following the Brexit vote, but ministers have remained tight-lipped about the future system.
Last month, Home Secretary Amber Rudd hinted that the regime could include measures to reduce the number of migrants who arrive from the EU looking for work.
Figures show that an estimated 82,000 EU immigrants came to the UK to seek employment in the year to June.
The Government's Brexit white paper says the new system will be designed to help fill skills shortages, while any approach could be "phased in" to give businesses and individuals time to plan and prepare for changes.
A Home Office spokeswoman said: "Voters made it clear during the referendum that they wanted the country to take back control of immigration.
"This Government will deliver on that by building an immigration system that works for everyone.
"Once we have left the European Union it will be the Government that sets our immigration rules."