The seventh World Happiness Report ranked the UK in 15th out of 156, one place above Ireland, and a rise of four places on the previous year’s report.
By contrast, Ireland slipped from 14th to 16th, above the likes of Germany (17th), Belgium (18th) and the United States (19th).
The happiest country, according to the report – for the second year running – is Finland, ahead of Denmark, Norway, Iceland and the Netherlands.
New Zealand (eighth) and Canada (ninth) are the only non-European nations inside the top ten.
The scores are based on individuals’ assessments of their own lives over a two-year period.
The evaluation asks up to 3,000 survey respondents in each country to place the status of their lives on a “ladder” scale ranging from zero to ten, where zero means the worst possible life and ten the best possible life.
The report sees South Sudan replacing Burundi as the least happy country, ahead of the Central African Republic and Afghanistan.
Separate data on GDP, life expectancy, generosity, social support, freedom and corruption is also included in the report, but does not contribute to the overall happiness ranking.
It shows Ireland (sixth) ranks above the UK (ninth) for social support, GDP (sixth for Ireland compared with 23rd for the UK), and healthy life expectancy (20th compared with 24th). Ireland also has a higher ranking for perceived freedom to make life choices (33rd) ahead of the UK (63), and freedom from corruption (tenth compared with 15th).
But the UK has one of the best generosity rankings (fourth) of all countries, ahead of Ireland in ninth. It claimed 72.3 per cent of UK respondents said they had donated money to charity in the past month, compared with 69.9 per cent of Irish people.
The report cites results from a study into political voting and happiness, published in the European Journal of Political Economy in January, which identified those who were dissatisfied with life overall in the UK were around 2.5 percentage points more likely vote to leave the European Union.
The UN report adds, using data from the United Kingdom, that the likelihood of people voting also increases as they become happier, with a one-point increase in life satisfaction associated with a 2 per cent increase in the propensity to vote in an upcoming election.
The report comes a day after Office for National Statistics figures showed record numbers of people are in work, while the UK’s jobless rate has fallen below 4 per cent for the first time since 1975.
Average earnings increased by 3.4 per cent in the year to January, down by 0.1 per cent on the previous month but still outpacing inflation.
However, one of the report’s authors, Professor Richard Layard of the London School of Economics, and co-founder of UK charity Action For Happiness, said: “If governments want to stay in power they should take the happiness of the people more seriously than economic measures.
“It’s essential our leaders look beyond narrow financial measures and focus on the wider set of factors that really affect the well-being of the nation, and especially mental health.”