The country's population rose by 470,000 last year, the highest annual growth rate for nearly 50 years, statistics released today showed.
The UK's population stood at 62.3 million in the year leading up to mid-2010, up 0.8% on the previous year, the figures released by the Office for National Statistics (ONS) found.
The increase is in line with previous years over the last decade, and for the third year in a row natural change has been the cause rather than immigration.
Natural change (the difference between births and deaths) accounted for 52% of the UK population growth in the year to mid-2010, the main reason behind this being the number of births.
In 2009/10 there were 134,000 more births than in 2001/02.
Statisticians said this is due to there being more women in the key childbearing ages of between 15 and 44.
The number of migrants entering the UK remains at similar levels seen over the last six years, with 574,000 people coming to the country from abroad last year.
The ONS findings show that past migration has contributed to the increase in annual births in the UK since 2002 due to the increasing population of non UK-born women who tend to have more children than their UK-born counterparts.
While there were 12.3 million women of key childbearing age in 2000/01, in 2009/10 there were 12.5 million.
Another factor is the number of women born in the 1960s and '70s who put off having children and are now having children at older ages than in the past.
The lower number of deaths can be attributed to higher mortality rates due to medical advances, with circulatory diseases having seen the greatest fall in age-related mortality.
In particular, the number of men aged over 85 has increased.
The findings also show that net migration, the difference between immigration and emigration, has risen compared with the year before.
The country's population increased by 230,000 last year, with 574,000 immigrants coming to the country compared with 344,000 people who migrated overseas.
This is largely down to the fall in emigration of British citizens as figures from 2008/09 show that 386,000 left the UK then.
Prime Minister David Cameron and Home Secretary Theresa May have said they want to bring annual net migration down to just "tens of thousands" by 2015.
However a report released by Oxford University's Migration Observatory last week said it is thought they will only achieve half the desired effect at best.
None of the information released today relates to the recent 2011 Census.
Statisticians said the population's usual annual growth rate is 0.6%. Last year's 0.8% growth rate is the highest since the year leading up to mid-1962.
In response to today's figures, Immigration Minister Damian Green said: "This is yet more evidence of the impact that a decade of uncontrolled migration has had on the UK.
"We are in the process of fixing the immigration system we inherited to ensure that any migration-related population growth is sustainable and brings benefits to the UK.
"Net migration has been too high but the controls and reforms we are introducing will bring it back down to the tens of thousands."