Dick Van Dyke, who is currently filming Mary Poppins Returns, which is scheduled for release next year, has warned of his fears over the effects of “scary” video games and films on young children.

The 91-year-old actor, who will make a cameo appearance in the upcoming film, describes these activities as a far cry from the free-spirited, kite-flying, carousel-riding world of the two children, Jane and Michael, in the original Mary Poppins.

Van Dyke believes video games incite violent behaviour and that big-screen violence is affecting impressionable young people who “idolise it as a romantic way of life”. He has no doubt Walt Disney would have been horrified by the explicit depictions of blood, gore and killing in some of the contemporary productions created to entertain children. “He would have spoken out about it,” he said.

Van Dyke rose to prominence in films including Bye Bye Birdie, Mary Poppins and Chitty Chitty Bang Bang, as well as his TV sitcom The Dick Van Dyke Show. His role as Bert, the charming chimney-sweep in Mary Poppins, is perhaps the best known and, in the sequel, he will play the part of Mr Dawes Jr, chairman of Fidelity Fiduciary Bank, alongside Emily Blunt as the eccentric nanny.

Commenting on why the industry rarely makes films with such innocence as Mary Poppins, he said: “We lost Walt Disney, for one thing. Walt was a child at heart. He had such creativity and imagination. We said we were both children looking for our inner adults.”

Disney knew how to thrill children with fantasy, rather than reality, he added. “Walt said kids like to be scared. It’s a delicious feeling. But he did it with witches, evil queens and things like that. Now it goes into blood and violence.”

He argued that children’s films from Hollywood’s so-called golden age taught morals and manners: “When I was a teenager, I modelled myself after the way Fred Astaire or Cary Grant dressed. Now kids emulate street gangs. They like to dress like hoods. That’s just a reversal. They’re picking the wrong role models.”

So many productions today are “all gunfire and killing”, he said. “Violence and entertainment have almost became interchangeable.” He contrasts screen depictions of young people driving cars in a “crazy” way with films of the past, where a family would be driving along the highway singing: “All that rubs off on kids.”

There is some research to show that observing aggression increases the likelihood of a child mimicking. One study found that high levels of violence in shows such as Buffy the Vampire Slayer and Pokémon could make children more aggressive.

Such research adds to Van Dyke’s frustration when film-makers tell him that screen violence has no effect on children: “We know that isn’t true. I remember walking out of movies that were uplifting and feeling inspired. We’d go to a cowboy movie, we’d come home playing cowboys. It does affect one.”

He has tried in vain to raise his criticisms with producers: “They’re all in their 20s. They, of course, don’t think they’re doing any harm.”

Asked to single out some examples of violent children’s productions, he said that “almost any of them” could be mentioned. Even the Harry Potter films are too violent, he believes: “They’re wonderfully entertaining, but they’re kind of scary. Too scary.”

Depressingly, he senses that screen violence will only worsen: “I fear for my grandchildren. It’s all about the money and pandering to the lowest possible taste. That’s what’s happened, unfortunately. I don’t think anyone takes any responsibility.”

Yet he is inundated with letters from young people, aged eight upwards, who write to him after watching Mary Poppins and other such films from Hollywood’s past.

He said: “They ask ‘why aren’t there movies like that now?’ ‘What has changed?’ Even kids sense that there’s something gone wrong.”

Of his own films, Mary Poppins is perhaps his favourite. “I had probably the most fun. It was hard work, but something magical happened every day. It was a glorious thing to have done.

“There was a great spirit about it. Part of that was Walt, of course. He was just spurring us on and complimenting us. He let us be free with it, and that comes across in the film. It has that spirit.”