Britain's net migration from the European Union rose to 184,000 last year, partly fuelled by a jump in arrivals from Romania and Bulgaria, the government said on Thursday.
Estimated net migration of EU citizens in the 12 months to December was up from 174,000 in the previous 12 months and equalled the highest 12-month total recorded, according to data from the Office for National Statistics.
The rise was spurred by net migration of 102,000 in citizens of Bulgaria and Romania, but the ONS said the change in total net migration from the EU was "not statistically significant."
Immigration is expected to be one of the two main issues - along with the economy - in the final four weeks of campaigning before Britain holds an in-out referendum on its EU membership on June 23.
Britain's overall net migration rose to 330,000 in the year to December, including net migration of 188,000 from non-EU states, down from 194,000 in 2014.
Estimated total arrivals of EU citizens stood at 270,000 in 2015, up from 264,000 in 2014, while total arrivals of non-EU citizens fell by about 10,000 to 277,000 last year, the ONS said.
In the year to March, about three-quarters of the 826,000 new registrations for national insurance numbers - which allow people to work in Britain legally - were for EU citizens. They included 179,000 for Romanian citizens and 40,000 for Bulgarian citizens, it said.