Brexit migrant 'spike' warning from MPs
There could be a spike in UK migration ahead of Britain's withdrawal from the European Union and the possible end to free movement rights, MPs have warned.
The Home Affairs Committee urged the government to state an "effective cut-off date" for when EU citizens in the UK would be granted the right to stay.
It added there could be fresh delays and backlogs in the immigration system if more people tried to enter the UK.
Ministers said it would be "wrong" to set out details before exit talks.
The government has confirmed it will seek curbs on free movement rules that currently give EU nationals the right to live and work in other member states.
'No bargaining chips'
But it has said it is not possible to give a firm guarantee about the status of EU nationals currently living in the UK without a reciprocal pledge from other nations about British nationals living on the continent.
The committee's report said the outcome of the 23 June referendum, in which Britain voted to leave the EU, had placed EU nationals living in the UK "in a potentially very difficult and uncertain position".
"Past experience has shown that previous attempts to tighten immigration rules have led to a spike in immigration prior to the rules coming into force," the MPs said.
"EU citizens living and working in the UK must be told where they stand in relation to the UK leaving the EU and they should not be used as bargaining chips in the negotiations."
By Danny Shaw, home affairs correspondent
Every three months, the Home Affairs Committee meticulously documents the progress made by immigration officials in dealing with asylum cases, processing visa applications and removing foreign national offenders.
It's usually a depressing read, with examples of inefficiencies, backlogs and delays.
Today's report is no exception - but with an extra complication.
Britain's looming exit from the European Union raises the possibility of a sudden influx of EU citizens to the UK anxious to claim their right to residence.
If, as the report suggests, a "cut-off date" months or two years into the future is identified it's hard to see how a "surge" in arrivals can be prevented.
Name a date in the past - 23 June for example - and there'll be howls of protest from those who arrived afterwards.
Dr Swati Dhingra, from the London School of Economics, told BBC 5 live the rise in the national living wage in the UK might encourage people to travel to the country.
She also said if there was a cut-off date "a lot of people might think, if they want to move to the UK - now is the time".
The report said the most obvious cut-off period would be the date Article 50 - the formal mechanism to leave the EU - is triggered, or when the UK actually leaves the bloc.
It said the first step to establishing where EU nationals in the UK were living and working was through National Insurance numbers or a system of registration, and the process needed to start quickly.
A government spokesman said: "We are about to begin these negotiations and it would be wrong to set out further unilateral positions in advance. But there is clearly no mandate for accepting the free movement of people as it has existed up until now."