The UK population rose by a record one percent in the year to mid-2023 and by 1.2 million over a two-year period, with immigration the key driver, official data showed on Tuesday.

An estimated 68.3 million people lived in UK in mid-2023 -- an annual increase of 662,400 or 1.0 percent -- according to figures from the Office for National Statistics (ONS), the UK's statistical institute.

It is the largest annual percentage and numerical increase since comparable data began in 1971 and comes with the UK government facing political pressure over migration levels, as well as the provision of housing and services.

The new Labour government has already had to deal with the country's most serious rioting in a decade, which was attributed to anti-immigrant groups.

"Net international migration was the main contributor to population increase for all four countries of the UK in the year to mid-2023," said the ONS.

The statistics agency estimated that 1,185,600 people immigrated from outside the UK, with 508,300 emigrating in the year up to mid-2023, making net international migration 677,300.

Some 16,300 more deaths than births were recorded over the same period -- the first time since 1976 that there has been a negative natural change in the UK population, with the exception of Covid-hit 2020.

The population is estimated to have risen by 1,281,700 in the two years up until mid-2023, more than the number of people that live in Birmingham, the UK's second largest city.