The government is poised to announce a ban on junk food advertising online and before 9pm on TV from 2023, as Boris Johnson looks to deliver on his pledge to tackle the UK's growing obesity crisis.

The new measures, which will be some of the toughest marketing restrictions in the world, will heavily impact the more than £600m spent by brands on all food advertising online and on TV annually.

The 9pm pre-watershed ban on advertising TV products deemed to be high in fat, salt and sugar (HFSS) could cost TV broadcasters such as ITV, Channel 4, Channel 5 and Sky more than £200m a year in revenue.

The online ad ban would affect all paid-for forms of digital marketing, from ads on Facebook to paid-search results on Google, text message promotions, and paid activity on sites such as Instagram and Twitter. It is estimated that more than £400m is spent on advertising food products online in the UK annually.