Data using the key measure of immigration to the UK shows it has fallen from record levels, official figures reveal.
Overall net migration was running at 323,000 in the year to September 2015 - 13,000 lower than the previous two quarters when it was at an unprecedented high of 336,000.
The data also revealed a fall in net migration of EU citizens compared to the previous three months - down from 180,000 to 172,000.
The data, published by the Office for National Statistics days after David Cameron fired the starting gun on the EU referendum, showed that 165,000 citizens from the bloc came to Britain for work-related reasons.
Net migration is the difference between the number of people arriving and leaving the country.
Nicola White, Head of Migration Statistics at the ONS, said: "Net migration to the UK in the year ending September 2015 was 323,000.
"Statistically, this is not a significant change from the previous peak level of 336,000 published in the last quarter, nor the level of 292,000 estimated in the year to September 2014."
It is the first time that estimated annual net migration to the UK has fallen since the end of 2013.
However, the level is still substantially above the Government's objective of bringing it below 100,000.
It also means annual net migration has been running at above 300,000 for almost two years.
Net migration for EU citizens in the year to September was higher than the previous 12 months, when it stood at 158,000.
Immigration of EU citizens - simply the numbers arriving - was estimated to be 257,000 in the year to September, a small increase on the 246,000 in the previous 12 months.
However, the ONS said there was a "statistically significant" increase in immigration of Bulgarians and Romanians compared with the year before, with the number arriving up by 15,000 to 55,000.
Migrants from the two countries now account for more than a fifth (21%) of total EU immigration, compared with 16% in the year to September 2014.
Restrictions on Bulgarians and Romanians working in the UK were lifted in January 2014.
Madeleine Sumption, director of the Migration Observatory at the University of Oxford, said: "Free movement within the EU is not the only driver of recent high levels of net migration, but it has played an important role.
"While EU migration is a defining issue in the referendum debate, the truth is that it's difficult to predict EU migration levels with confidence in either the stay or leave scenario.
"Whether Brexit would reduce migration will depend in part on the treaties and policies that followed, and these cannot be known in advance."
She added: "Sustained high levels of net migration raise the question of whether we are experiencing a temporary peak or a 'new normal' in the UK.
"In the short term, the UK remains an attractive destination with low unemployment and robust job growth so there's no reason to expect a dramatic change to migration levels.
"In the long run, migration is much harder to predict. It will depend on many different factors from future policy changes to economic growth in other countries."
Immigration Minister James Brokenshire said: "We remain committed to reforms across the whole of Government to bring migration down to sustainable levels, which is in the best interests of our country.
"Our reforms have cut abuse in the student and family visa systems and raised the standards in work routes.
"The Prime Minister has re-negotiated the UK's position within the EU to close backdoor routes into the UK and exert greater control over EU migration by tackling the artificial draw of our welfare system. We will also insist on tougher immigration controls when new member states join the EU, to stop the mass migration that we have seen in the past.
"But net migration remains too high and there is still more work to do.
"The Government will continue to do more to ensure that Britain's businesses find and develop the talent they need within the UK, while ensuring they still have access to the top talent from abroad to help them prosper.
"In addition, our new Immigration Bill, which is currently going through Parliament, will provide new powers to tackle illegal working and make it harder than ever for those with no right to be in the UK to stay here."