Facebook is losing a share of teen users to Instagram and Snapchat in the UK and the US, as the image-focused platforms continue to attract younger audiences.

New research from eMarketer has estimated that Facebook has around 32.5 million users in the UK, making it the most popular social network – but it is losing younger eyeballs to Snap and Instagram.

In the UK, among the 12-to-17 and 18-to-24 age brackets, Facebook’s user numbers will decline by 2.8% and 3.1% respectively this year according to eMarketer.

Across all age groups, more than a quarter of the UK population will log on to Instagram at least once a month by the end of 2017 meaning in total 16.7 million people will be regular Instagram users; an increase of 35% on 2016.

21% of Brits will be signing into Snapchat on a monthly basis before the year is out, but while Snap will enjoy 20% growth on last year's UK figures, eMarketer has dialed down its long-term forecasts for the Venice Beach-based firm indicating that Instagram’s attempts to woo younger users by nabbing several of Snap’s core features is reaping fruit.

“Facebook is still the big winner in social media,” said Bill Fisher, eMarketer’s UK senior analyst. “But it will be slightly concerned that younger people in the UK are having their heads turned by Snapchat. Of course, its ownership of Instagram is softening the blow, and it will be further enthused to see Instagram’s longer-term prospects looking even better than Snapchat’s.”

In the US, eMarketer has reduced its usage estimates for US monthly Facebook users aged 12 to 17 and 18 to 24. Stateside, Snapchat's growth figures have been adjusted higher for all but the oldest age group, with the biggest upward revision made to the 18-to-24 group. That young adult cohort will see usage escalate 19.2% this year.

Despite stalling in the teen sector Facebook continues to power ahead in all other areas, recently posting a 45% gain in revenues to reach $9.3bn fuelled primarily by mobile growth.