The population of the UK has passed 65 million for the first time after rising by more than half a million in a year, official figures have revealed.
Natural growth - more births than deaths - of 171,800 and net international migration of 335,600 helped push the number of people living in the country to an estimated 65.1 million as of the middle of 2015.
This was a jump over the year of 513,000, or 0.8%, while the figures mean the population has increased by around 4.7 million in 10 years.
The Office for National Statistics said the rise over the 12 months to mid-2015 was similar to the average annual increase seen in the last decade.
Population change due to natural change is at its lowest level since the year to mid-2006, the ONS said.
Its report said: "The number of births has decreased on last year's figure and is below the average for the period, while there was an increase in the number of deaths since last year, partly attributed to flu outbreaks in early 2015."
Meanwhile, an increase in immigration (up 53,700) and a smaller decrease in emigration (down 22,300) both contributed to the increase in net international migration compared to that seen in the year to mid-2014.
International migration inflow is at its highest since the year to mid-2007, the ONS said, while outflow is at its lowest since comparable records began in 2002.
The figures indicate that migration accounted for just under two-thirds (65%) of the annual change.
In addition to the direct impact on the size of the population, current and past international migration also has indirect effects on the size of the population as it changes the numbers of births and deaths in the UK, the ONS report said.
An increase of 5,800 people in the armed forces and prison populations also contributed to the growth.
The figures were released hours after the polls opened in the EU referendum and come after a campaign which has been dominated by debate over immigration.
Simon Ross, chief executive of charity Population Matters, said: "The UK population is growing faster than even the concerning trend of recent years.
"Near-record net migration and an excess of births over deaths, to which migration also contributes, are combining to keep the UK near the top of the European population growth league table."
Alp Mehmet, vice chairman of campaign group Migration Watch UK, said: "These figures confirm that our population is growing by around half a million annually - the equivalent of a city the size of Liverpool every year.
"As the population grows beyond our capability to provide for it, pressure on housing, schooling, healthcare and transport will become ever more critical. This is unacceptable to the majority of the public who wish to see net migration reduced."
England saw the biggest jump in population, with a rise of 469,700, or 0.86%, to 54,786,300.
The population of Scotland increased by 25,400 (0.47%) to 5,373,000; Wales rose by 7,100 (0.23%) to 3,099,100; and Northern Ireland was up by 11,100 (0.60%) to 1,851,600.
The older population continues to grow, with more than 11.6 million people - 17.8% of residents - aged 65 and over, and 1.5 million (2.3%) aged 85 and over.
Since mid-2005, the UK population aged 65 and over and aged 85 and over have increased by 21% and 31% respectively.
Vote Leave chief executive Matthew Elliott said: " The only way to get back control over our borders is to Vote Leave today.
"In the last 10 years, as many people as live in Birmingham have moved here from another EU country.
"That puts a huge strain on our NHS and our schools.
'If we Vote Leave, we can take back control and introduce a new Australian-style points-based immigration system."