The Home Office insisted British citizenship was a "privilege, not a right" and blamed the figures on "uncontrolled" levels of immigration under the last Labour government.
Around three quarters of the 818,000 new citizenships in the EU were granted in just six countries, according to Eurostat, the union's statistical office.
Britain topped the list with 23.7%, followed by Germany on 14%, France on 11.7%, Spain on 11.5%, Italy on 8% and Sweden on 6.1%.
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A shooting is reported to have taken place in the French city of Strasbourg, close to a Christmas market.
Irene O'Shea became the oldest female skydiver on Sunday when she took part in the charity jump in South Australia.
The prime minister said that contingency planning for no-deal had been increased in "recent days".