Video report by ITV News Midlands Correspondent Stacey Foster
Stephen Fry and Sandi Toksvig are among the celebrities to back a campaign arguing for subtitles to always be turned on to improve children's reading.
The group Turn on the Subtitles said research has shown having subtitles on when a child is watching television can double the chances of them becoming a good reader.
Mr Fry said: "The impact of the Covid-19 pandemic has meant that some children have actually taken a step backwards, a leap backwards in literacy, which is a worry and a tragedy."
He said turning on the subtitles was free and took 10 seconds, and encouraged everyone to take part.
Philip Schofield, Sir Lenny Henry, Rachel Riley, Sanjeev Bhaskar and Sally Hawkins are among the celebrities to endorse the campaign.
The campaign argues subtitles should be turned on for all programmes aimed at children aged between six and 10.
A testimonial on their website by Sir Lenny said: "Just turn on the subtitles. Extraordinary. Research has shown they can double the chances of a child becoming good at reading."The campaign's website claims there is a rich global body of evidence supporting their campaign.
They point to a study of 2,350 children where 34% became good readers with schooling alone. But, when exposed to 30 minutes a week of subtitled film songs, that proportion more than doubled to 70%.
They have also got the backing of Prime Minister Boris Johnson and former US President Bill Clinton.
Mr Johnson said "I think that the campaign is excellent" and said all departments that have a stake in children's education should look into it.
Turn on the Subtitles claims Netflix and Amazon are piloting permenent subtitles based on their campaign.
YouTube has also improved its subtitling on their children's platforms.
The campaign claims to be the world's biggest literacy project and is helping over 300 million children to learn to read.