Excluding Ireland, there are around 247,000 British citizens of pension age living in the EU compared with 85,000 EU citizens of pension age in the UK.
Given the UK’s “unique relationship” with Ireland, the ONS excluded the country from its report.
Figures from the Department for Work and Pensions (DWP) show that the number of UK state pension recipients living in other EU countries has risen steadily over the last five years, continuing a long-term trend.
In February 2017, the DWP paid around 340,000 pensioners living in the EU (excluding Ireland) the state pension.
There are 121,000 older Brits living in Spain, more than double the number 10 years ago.
This compares with around just 6,500 Spaniards over the age of 65 living in the UK.
The number of people in this age group moving to Spain has not gone up significantly since 2008, so the recent increase is likely to be due to people who have lived there for many years getting older, the ONS surmises.
In contrast, there are nearly four times as many Italians of pension age living in the UK than there are Brits in Italy.
The ONS explained that there have historically been relatively high levels of migration from Italy, especially in the 1950s, '60s and '70s, and most people who moved to the UK in those years are now aged 65 and over.
Similarly, the older people from Poland who live in the UK, significantly outnumbering the number of older Brits living in Poland, are mainly long-term residents rather than more recent migrants.
Below is a table of the number of citizens over the age of 65 living in each country. Italy, Sweden and Poland are the only countries in which there fewer Brits compared with its' citizens living in the UK.
Tom Selby, senior analyst at AJ Bell, comments: “After the hurricane of uncertainty created by the shock Leave vote in June last year, we now appear to be in the eye of the storm.
"The number of UK citizens in receipt of the state pension in EU countries (excluding Ireland) has held steady since the referendum, suggesting the mass exodus some feared has yet to materialise.
“It may be that those considering returning to the UK are awaiting clarity on how the final deal will affect them, although for many retired expats whether or not their state pension continues to rise in line with the triple-lock will be just one of a number of factors to be considered.
“The value of annual increases in the state pension should not be underestimated, however, and could run into tens of thousands of pounds over the course of a person’s retirement.
“But ultimately it makes sense for people to hang tight until details of the Brexit deal become clear,” Selby said.