THE number of European Union nationals who are living in the UK has fallen, figures show.

Office for National Statistics (ONS) data for 2020 shows that within a year, the population of EU nationals in the UK dropped by 200,000, from 3.7 million to 3.5m.

Experts have said the Covid-19 pandemic and Brexit have likely been factors in people’s decision to move from or to the country.

An ONS spokesperson said: “Decisions to migrate are complex and a person’s decision to move to or from the UK will always be influenced by a range of factors, including social and economic reasons.

READ MORE: Brexit: UK only EU trading partner to see exports fall, data reveals

“It’s possible that the impact of the pandemic, alongside other factors such as the UK exiting the European Union, may have influenced the behaviour and decisions of the non-UK population living in the UK.

“This could include an increase in those leaving but also a decrease in those coming to live in the UK.”

Other sections of the population have remained stable, including non-UK-born residents of which there are 9.5 million, and non-British residents who total 6.1 million.

The current population of the UK is estimated to be around 67 million.

Polish continues to be the most common non-British nationality, making up 738,000 of residents. Romanian is the next most common at 384,000, followed by Irish, Indian and Italian.

India is still the most common non-UK country of birth with 880,000 people, followed by Poland with 691,000, and then Pakistan, the Republic of Ireland and Romania.

London continues to be the region with the largest proportion of people who were not born in the UK and are not British.

The National: The UK's departure from the EU was cited as a reason for people leavingThe UK's departure from the EU was cited as a reason for people leaving

Non-UK-born residents make up 37% of Londoners, and non-British people make up 22% of the capital’s population.

The local authority with the highest percentage of non-UK-born residents is Kensington and Chelsea (53%). This is a change from 2018 and 2019 when Brent had the highest.

Due to the pandemic, the way the ONS collects population data has changed which means it cannot be compared to previous years.

Jay Lindop, director of the Centre for International Migration at the ONS, said: “Our best estimates show that while non-UK born and non-British populations remained broadly stable in 2020, the number of people living in the UK with EU nationality fell.

READ MORE: Nancy Pelosi: Brexit deal with US 'unlikely' if Northern Irish peace is threatened

“However, the impact of the coronavirus pandemic on how our survey data were collected and the statistics produced means there is a high level of uncertainty around numbers below EU and non-EU level, which should not be compared against previous years.”

There are three main reasons for differences between nationality and country of birth.

People who are born abroad who decide to remain in the UK often apply to become British nationals.

Some who are born abroad already have British nationality because, for example, their parents were in the military and were based abroad when they were born.

Some who are born in the UK to migrant parents also take the nationality of their parents.

Meanwhile, new statistics indicate that one in 13 people living in Scotland last year were not British nationals.

Nearly 8% of the country’s population, about 406,000 people, were considered to be from overseas according to statistical estimates from the National Records of Scotland (NRS) for the year ending December 2020.

The figures suggest that six out of 10 (61%) non-British nationals living in Scotland last year were from the EU, about 247,000 people, while the remaining 159,000 were from outside the EU, with about 7,000 from the rest of Europe, 59,000 from Asia, and 93,000 from the rest of the world.

Poles were the most common non-British nationality in the year ending December 2020, with about 92,000 Polish nationals living in the country, equivalent to nearly one-quarter (23%) of non-Brits.

Next most common were people from the Republic of Ireland at 19,000 people; Italians, who numbered 18,000; Nigerians at 17,000 and Germans at 14,000, the estimates indicate.

The National: Edinburgh is among the top Scots cities for non-BritsEdinburgh is among the top Scots cities for non-Brits

Aberdeen, Edinburgh and Glasgow had the highest concentrations of non-Brits, at about one in five people (20%) in Aberdeen City, followed by 19% in the City of Edinburgh, and 12% in Glasgow city, the NRS added.

In 2004, just 52,000 people in Scotland are estimated to have been from the EU, while 74,000 came from outside the EU.

The full report: Population by Country of Birth and Nationality for Scotland, 2020, can be accessed on the NRS website.

The estimates are sourced from the Office for National Statistics’ Annual Population Survey (APS), which had a sample size of 26,000 for Scotland, and because it is a survey there is “sampling variability and a degree of uncertainty with the results”, the NRS said.

READ MORE: UK Government to take 'Brexit opportunity' to bring back imperial measures

The NRS urged caution in comparing the figures from this report to previous years owing to a new weighting methodology which was introduced because of the coronavirus pandemic.

It said the pandemic meant face-to-face interviewing for the Labour Force Survey, on which the APS is based, was suspended in March last year in favour of telephone interviews.

But this meant fewer responses from people who rent their accommodation and those with a non-UK country of birth or nationality, meaning they were less-well represented in the sample.

Statisticians tried to correct for this using Pay-As-You-Earn (PAYE) real-time information to allow for changes to the survey collection methods but said comparisons with previous years could still be subject to “greater uncertainty”.