The UK's population has grown to 60 million for the first time, Government figures confirmed today.
There was a sharp 0.6% rise of 375,000, taking the figure to 60.2 million by June last year, the Office for National Statistics said.
Fuelled by net international migration, this is the biggest annual rise in numbers since 1962 and the fastest growth rate since 1965.
In the year to mid-2004, there had been a 0.5% rise amounting to an average increase of 0.4% over the five years to 2004.
From 1989 to 1999 there had been a 0.3% increase.
The key trigger behind the spike in population growth has been the net international migration - the difference between migration into and out of the UK.
The migration of citizens from nations which joined the European Union in May 2004 has been the driving force behind the increase.
In 2004-05, the first full year of their membership, net migration of citizens from these accession countries who stayed for at least a year was 74,000, compared with 10,000 in 2003-04.
Net international migration rose from 167,000 in 2003-04 to 235,000 in 2004-05.
This was the highest level since estimates of Total International Migration were first produced on the current basis in 1991.
Migration into the UK was around 59,000 more than in the previous mid-year period, a rise of 11%, and migration from the UK fell by 2%, or 8,000 people.
Natural change, the difference between numbers of births and deaths, increased from 104,000 in 2003/04 to 127,000 in 2004/05.
There were 10,000 more births and 12,000 fewer deaths in 2004/05 than in 2003/04, the ONS said.
At 0.8%, Northern Ireland had the fastest population growth.
England's grew by 0.7%, Scotland's by 0.3% and Wales by 0.2%.
England now has a 50.4 million-strong population, while Wales was 3 million in 2005, Scotland 5.1 million and Northern Ireland 1.7 million.
The UK also has a record 1,176,000 people aged over 85 - 6% growth of 64,000 in the year to 2005.
They now make up 2% of the population and include 352,000 men and 824,000 women.
This age group had increased from 873,000 in 1991 to 1,130,000 in 2001, but fell slightly between 2001 and 2003, reflecting a dip in births during the First World War.
The working-age population, 16 to 64 for men and 16 to 59 for women, rose by 304,000 from 37.1 million to 37.4 million between 2004 and 2005.
The total number above working age rose by 119,000 from 11.1 million to 11.2 million.
The number of under-16s dropped slightly from 11,646,000 to 11,598,000 between 2004 and 2005, having previously exceeded 12 million in the 1990s.
This group now makes up 19.3% of the population and includes 5,946,000 boys and 5,652,000 girls.
In 1995 this group made up 20.7% of the population.
Migrants are helping to boost the UK's population not only through the number of adults but also through the number of births.
Peter Goldblatt, of the ONS, said: "Had there been no migration whatever, the population of the country would have had fewer births. The numbers of births would not have gone up.
"Migrants are fuelling the reducing numbers of women at fertile age and migration has contributed to the increases in the numbers of births."