The European Union (EU) wants the UK to keep its borders open to free movement and uncontrolled mass migration from the bloc for another two years.
If Brussels has its way, all migrants arriving in those two years would be able to stay on indefinitely.
It could trigger a sudden spike in immigration as European migrants rush to get here before Britain takes back control of its borders.
EU sources revealed the demand to The Sun, claiming it emerged from a seminar of senior officials on Wednesday, chaired by the EU’s chief Brexit negotiator Michel Barnier.
Senior MPs have already called on Prime Minister Theresa May to set the cut-off date for allowing new arrivals to stay as the day of the Brexit referendum, June 23 last year.
This date would guarantee the rights of some 3.2million EU migrants already here, and was called for in a report by senior Remain and Leave MPs in December.
Leave campaign boss and former Labour minister Gisela Stuart, who chaired the report, said it would “limit any ‘pull factor’ for EU citizens not already in the UK”.
A third cut-off date option discussed by ministers is the date Mrs. May triggers the ‘Article 50’ exit talks, which is expected in mid-March.
The PM’s official spokesman said: “We’ve been clear that the PM sees it as a priority to grant reciprocal rights to EU citizens as long as rights for Britons living in the EU are recognised when negotiations get under way.
“The date will be one of the things we discuss with other nation states.”
Frenchman Mr. Barnier has taken a hardline approach to Brexit talks so far.
This Monday, it was reported he was plotting to ban talks on a future trade deal with the UK until the government responds to his demands to pay a £51.2 billion (€60 billion) divorce bill.
It was also claimed he wanted to withhold confirming the status and future of British expats living in the other 27 members states until his demands are met.