The BBC was heavily criticised over dramas Quirke and Jamaica Inn

Miss Leeming said young stars need to improve their spoken English

For nearly a decade in the 1980s, the nation learned of the day’s events from her clipped tones and clear elocution.

But former newsreader Jan Leeming admits the diction of actors and presenters has become so poor, she has to rely on subtitles to understand modern television.

And writing in today’s Daily Mail Weekend magazine, she called on broadcasters to enrol their young stars on courses to improve their spoken English.

Former BBC newsreader Jan Leeming, pictured, said the quality of diction on TV has declined dramatically

Miss Leeming, 72, who spent seven years as a newsreader for the BBC, writes: ‘There’s been a noticeable rise in poor diction on TV over the last decade and it’s getting worse. It’s particularly evident among younger actors and presenters who, infuriatingly, so often swallow or don’t end their words.

‘The solution, I believe, is for TV networks to enrol today’s young presenters on courses to help them speak with greater clarity. I’m not calling for them to be made to recite phrases like “How now, brown cow”, as in the past – but simply to be taught clear enunciation and voice projection.

‘After all, they’re in the communication business so, to put it bluntly, don’t they have a duty to make themselves understood by viewers?’

Miss Leeming, whose father enrolled her in speech and drama classes as a child to neutralise her south-east London accent, denies her age has anything to do with her difficulty hearing.

She said: ‘I can hear the kitchen cat flap go from my sitting room. But all too often I find myself switching on the subtitles in order to understand the English.’

Miss Leeming praised Channel 4 News anchor Jon Snow, pictured, for his ability to read the news

The former presenter, who has been married five times, refused to name newsreaders she believes fail to speak as clearly as they should – although she did single out Channel 4 News anchor Jon Snow for praise – but is concerned there are some who ‘put the emphasis on the wrong words when reading a bulletin.’

This is not the first time the pronunciation of modern television stars has come in for criticism.

Earlier this year, actors in BBC dramas Jamaica Inn and Quirke were accused of mumbling their lines and that their thick accents were impenetrable. With the former programme attracting nearly 2,200 complaints from disgruntled viewers.

And in an interview last year, BBC Director-General Tony Hall said: ‘I don’t want to sound like a grumpy old man, but I also think muttering is something we could have a look at.

‘Actors muttering can be testing. You find you have missed a line. You have to remember you have an audience.’

Miss Leeming, who presented the 1982 Eurovision Song Contest, also singled out television actors for particular criticism.

She recounted how she recently watched a comedy where half the parts were played by theatre actors and the other half by soap stars.