LONDON — The population grew at the fastest pace for nearly half a century last year, adding almost half a million people due in large part to a high birth rate, official data showed on Thursday.

The population stood at 62,262,000 in mid-2010 which is an increase of 470,000 compared with a year earlier, according to figures released by the Office for National Statistics (ONS).

It was the highest growth rate since 1962.

The population increased by 0.8 percent, compared to an average annual growth rate of 0.6 percent in recent years, according to the ONS.

Natural change, the difference between births and deaths, was the largest contributor to population growth, said the ONS.

It accounted for 52 percent of the growth, with 134,000 more births last year than eight years earlier, the figures showed.

There were more women in the key childbearing ages of 15 to 44 and some women born in the 1960s and 1970s were now having children after putting it off in their younger years, said the statisticians.

Migration also played a role in the high birth rate, said the ONS.

"The number of births has increased partly due to rising fertility among UK born women and partly because there are more women of childbearing ages due to inflows of female migrants to the UK," it said in a statement.

There was also a lower number of deaths due to medical advances, the ONS said.

Between 1999 and 2008, migration had been the main contributor to population growth in Britain but a high birth rate has been the biggest factor in the past two years.

Net migration to Britain stood at 230,000 last year, with 574,000 immigrants coming to the country compared to 344,000 people who migrated overseas.