The number of EU nationals given certificates confirming their right to live in the UK permanently has jumped to its highest level in at least a decade, figures show.
A total of 7,307 documents certifying permanent residence were granted to people from the bloc in the three months to the end of June.
This was the highest quarterly tally since the current official data set started in 2006 - and more than four times the number in the equivalent period last year.
The combined total for the first half of this year was 12,503 - compared to 4,569 granted from January to June in 2015.
The figures for the most recent quarter cover the weeks leading up to and days immediately after the Brexit vote, which has prompted intense scrutiny of the status of EU migrants already living in Britain
Madeleine Sumption, director of the Migration Observatory at the University of Oxford, said: "Given the uncertainty about how Brexit will affect the status of EU citizens already living in the UK, it's not surprising that there was more interest in permanent residence in the run-up to the referendum.
"That said, we should expect much bigger increases over the next few months."
She added: "The vast majority of EU citizens in the UK don't yet have any documentation proving permanent status.
"About 12,500 EU citizens were granted permanent residence in the first half of 2016, but more than two million have lived in the UK for more than five years and so are potentially eligible to apply.
"The big question therefore is what happens next. The government has committed in principle to protecting the rights of EU citizens already living here, but the administrative task of doing this quickly and efficiently will be huge."
EU citizens who have lived continuously in the UK for at least five years automatically have a permanent right to live in Britain.
People from countries in the European Economic Area - EU states as well as Iceland, Liechtenstein and Norway, plus Swiss nationals - can apply for a document which confirms their right of permanent residence in the UK. Family members of EEA citizens can apply for a permanent residence card.
Applicants from a group of eight nations which joined the EU in 2004 - Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Slovakia and Slovenia - accounted for a total of 3,637 permanent residence documents granted in the three months from April, while 1,262 were given to Romanians and Bulgarians. Another 2,408 went to people from other EU states.
Overall, in the second quarter of this year a total of 10,121 permanent residence documents and cards were granted - nearly three times the level in the same three months of 2015.
A rule change meaning that from November someone applying for British citizenship who claims to have permanent residence must provide a certifying card or document may have contributed to the rise.
The figures - published by the Home Office among a tranche of data last week - also show there were 3,538 refusals for permanent residence cards or documents in the three months, while 1,422 applications were recorded as invalid.