The minister in charge of Brexit has suggested a cut-off date for giving migrants from Europe leave to remain status to avoid a "surge" of people entering the country between now and leaving the EU.
David Davis has said he will seek a "generous settlement" for EU citizens already in the UK and expats in Europe.
"We may have to deal with that," he said, speaking to the Mail on Sunday on the possibility of an increase in the number of Europeans coming to the UK before leaving the bloc.
He said there are "a variety of possibilities" and "we may have to say that the right to indefinite leave to remain protection only applies before a certain date".
However, a call on a cut-off date would have to be based on "reality, not speculation" he said.
His comments sparked outrage from others, with Liberal Democrat leader Tim Farron saying the remarks were "just thrown out for a cheap headline".
"It’s an utterly un-British thing to do and our society is richer, better and more entrepreneurial for immigration and for this diversity," Farron added.
The Scottish National Party's Europe spokesperson Stephen Gethins slammed the Conservative party for using EU nationals as "bargaining chips" and dubbed the actions "shameful".
"Davis' comments lay bare the priorities of Theresa May's 'nasty party' cabinet and once again show how unprepared the Leave side and the UK government were for the possibility of a Brexit vote," Gethins added.
Meanwhile, mayor of London Sadiq Khan added: "I have been clear that the one million Europeans living in London, who make a huge contribution to our capital by working hard, paying taxes and contributing to our civic and cultural life, are welcome here. We value their enormous contribution and that should not change as a result of the referendum."
The two year window between invoking Article 50 and the UK actually leaving has raised concerns that there could be an upswing in the number of people coming to the UK from Europe in a race to beat new immigration controls.
The status of EU nationals living in the UK and Brits living in Europe is one of the many key points of negotiating the country's exit from Europe.