Every British citizen should be given a unique "person number" in a register of the national population to help the Government deal with immigration, a thinktank has said.
The system would not require ID cards, but would give ministers much more reliable oversight of population changes and movement across borders, said Policy Exchange.
Author David Goodhart said the recent vote to leave the European Union was driven in part by public unease over the Government's inability to be sure how many people were in the country and where they were living.
But the idea was denounced as "ID cards by the back door" by Liberal Democrat leader Tim Farron, who said border exit checks introduced under the coalition government already gave ministers the tools they need to monitor who was coming into and out of the country.
The Policy Exchange report noted that most UK citizens already have several identifiers, such as NHS numbers, National Insurance numbers and passport numbers, but the information relating to them is held in different places and is not shared between databases.
Developing a single "person number" for every citizen would help the Government combat illegal immigration and allocate resources to areas of the country which experience surges of incomers, it said.
The number - probably based on NHS numbers - would distinguish between full and temporary citizens, such as students and short-term migrant workers on limited-time visas.
Report author David Goodhart said: "Roughly two million people arrive in the UK on visas every year and too many are overstaying. We have to urgently address the resentment that people feel about the fact that some migrants use Britain as a sort of economic transit camp.
"The Government needs to get a grip on who is coming into Britain, where they are living and what public services they are accessing. A British population register which differentiates between full and temporary citizens will help the Government concentrate rights, benefits and integration efforts on those who are making a full commitment to the country."
But Mr Farron said: "Brexit must not be used to bring in ID cards by the back door. One of the first actions the Liberal Democrats took in Government was to scrap Labour's authoritarian ID card scheme. The Conservatives must not endorse a report that could see a move to reintroduce a similar provision. If they do, they will be met with the strongest opposition.
"In Government we fought to introduce exit checks at the UKs borders in the face of opposition from Theresa May, so we know who is leaving, as well as who is arriving - I see no need to create a new database when we have already brought in a proper tool to do the job."