Net migration to the UK has fallen from record levels, official figures have revealed.
It is the first time the key measure of immigration has dipped since the end of 2013.
However, at an estimated 323,000, it remains more than three times above the Government's aim of less than 100,000 and has now been running at an annual level of more than 300,000 for almost two years.
One expert questioned whether sustained high levels of net migration are a temporary peak or a "new normal".
The data, published by the Office for National Statistics (ONS), sparked a fresh confrontation between the opposing camps in the EU referendum debate.
Home Secretary Theresa May said net migration was too high but insisted a deal struck by David Cameron will clamp down on abuse of free movement and "reduce the pull factor of our welfare system".
However, Ukip leader Nigel Farage claimed the UK "must leave the European Union to control our borders".
Estimated net migration - the difference between the number arriving and leaving - was 13,000 lower than the record high of 336,000 posted in the 12 months to both March and June.
When compared with the year to September 2014, overall net international migration was up by 31,000.
Nicola White, head of migration statistics at the ONS, said: "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."
Madeleine Sumption, director of the Migration Observatory at the University of Oxford, said: "Sustained high levels of net migration raise the question of whether we are experiencing a temporary peak or a 'new normal' in the UK."
The figures also showed:
:: Net migration from the EU was at 172,000 in the year to September. This was down compared with 180,000 for the year ending in June 2015, but higher than the 158,000 in the 12 months to September 2014.
:: An estimated 165,000 EU citizens came to Britain for work-related reasons. Of those, 58% had a definite job and 42% came looking for work.
:: Immigration - the number of people arriving - was an estimated 617,000, which was 2,000 higher than the year to September 2014.
:: The inflow of EU citizens was an estimated 257,000 in the year to September - up slightly compared with 246,000 in the previous 12 months.
:: There was a "statistically significant" increase in immigration of citizens of Bulgaria and Romania compared with the year before, up by 15,000 to 55,000. Migrants from the two countries now account for more than a fifth (21%) of total EU immigration.
The latest immigration figures came under particular focus as they were published days after Mr Cameron's EU renegotiation deal fired the starting gun on the referendum in June.
Employment minister Priti Patel, who is campaigning for Brexit, said: "The proposed deal will do nothing to reduce the level of immigration from the EU. The only way to take back control is to Vote Leave."
Lord Green of Deddington, chairman of campaign group Migration Watch UK, said: "Today's figures show that there is no sign of any let-up in the severe pressures of immigration on the UK."
Immigration minister James Brokenshire insisted the Government is committed to reforms to "bring migration down to sustainable levels".
He said: "The Prime Minister has renegotiated the UK's position within the EU to close back-door 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."
A Downing Street spokesman confirmed that Mr Cameron's "ambition" remains to bring net immigration into the UK below 100,000, but declined to put a timeframe on the target being met.