A major study has been ordered by the British government to look at the economic impact of ending free movement of EU workers.
The UK Home Secretary, Amber Rudd, wants to know whether some parts of Britain will be affected more than others, whether there will be skills shortages and the impact on seasonal jobs.
The study will be carried out by the UK's Migration Advisory Committee, a quango that advises the government there on immigration issues.
It is set to report by September next year.
In a letter to the committee's chairman, Professor Alan Manning, Ms Rudd said the government continues "working towards the goal of achieving sustainable levels of net migration".
And she said that under Brexit "we will be able to apply different immigration rules and requirements according to the UK's economic and social needs".
She said: "Leaving the European Union gives us the opportunity to take control of immigration from the EU.
"We will ensure we continue to attract those who benefit us economically, socially and culturally.
"But, at the same time, our new immigration system will give us control of the volume of people coming here - giving the public confidence we are applying our own rules on who we want to come to the UK and helping us to bring down net migration to sustainable levels.
"The study I am asking the Migration Advisory Committee to complete is a major step in ensuring we create a system that works in the best interests of the country."