Watchdogs have criticised Britvic for portraying an “unsafe activity” in one of its fruit juice ads and told to use a different approach in the future.

The poster showed a young boy swimming underwater while drinking juice. Safety guidelines advise against drinking at least one hour before swimming.

Britvic said that in the corner of the ad - in small print - it stated ‘Performed by professionals, under adult supervision. Please do not copy’.

The soft drinks firm said it had not intended young children to drink underwater and pointed out the warning on the poster.

The Advertising Standards Agency said the warning was not prominent and was likely to be overlooked.