LONDON -- Britain's population is projected to reach 70 million by 2029, the Office for National Statistics (ONS) said Thursday.

The official statistics agency says by 2026 Britain's total population is expected to increase by 3.6 million, or 5.5 percent from the current 65.6 million to 69.2 million.

The population is expected to pass the 70 million mark by 2029 and be 79.1 million by mid-2041, added ONS.

The projections show England's population is likely to grow by 5.9 percent over the period, compared with a growth of 4.2 percent in Northern Ireland, 3.2 percent in Scotland and 3.1 percent in Wales.

ONS said over the ten-year period, international migration into Britain is expected to account for 54 percent of the growth, with the remaining 46 percent coming from the higher number of births than deaths.

There figures also show there will be an increasing number of older people, with the proportion aged 85 and over projected to double over the next 25 years.