Stammering – a speech disability which can cause sufferers to "freeze" while speaking and struggle over words – can cause untold misery, but has often been mocked in television and films.

But new film The King's Speech, which will be released in January, lays bare the anguish and distress it can cause.

It stars Colin Firth as George VI and shows the monarch's battle to learn to control a stammer so he can fulfil the demanding public duties which fell to him after his brother Edward VIII abdicated.

The actor has described to the charity the British Stammering Association (BSA) his feelings about the testing role, and his own experience of vocal problems.

"It's amazing, if you go into an issue like this, just how many people will tell you they have it, or know someone who has it," he said.

"I'm very well aware that not many films have addressed this issue (stammering) except to make a mockery of it or to use it for comedy."

In reality the effects of stammering are far from amusing, says Norbert Lieckfeldt, himself a sufferer and chief executive of the BSA charity.

"People do learn to live with it and cope with it but its effects can be life-limiting. It masks ability; it masks your capacity, your intellect. It's a layer between you and the world which everything gets filtered through. It often results in depression because of the frustration it causes."

The charity is urging earlier diagnosis for children – citing research showing that speech and language therapy received by pre-school children with the problem may in many cases successfully eliminate the condition.

Firth also revealed to the charity the vocal problems he experienced during his 20s – successfully dealt with by surgery – which he believes gave him an insight into the condition. At the time he found he couldn't make himself heard when there were more than three people in a room or there was music playing.

"I couldn't cut through the way I wanted to, I couldn't express myself, my identity was completely stifled," he explains.

"It wasn't a stammer but it meant I couldn't be heard properly. And I remember a voice therapist I was talking to saying, 'don't underestimate how debilitating it is'. People appreciate the problem of blindness and deafness... (but) not being able to speak properly to people, in the way they expect, I think it's underestimated – the psychological damage it does."

A new campaign, Giving Voice, has been launched by the Royal College of Speech and Language Therapists to highlight the value of its services to those with a variety of speech problems – including children with speech and language impairment, such as a stammer.

"Stammering is a neglected condition in many ways and I think there is a general lack of understanding of the difficulties people go through with this problem," says Dr Rosemarie Hayhow, fellow of the Royal College of Speech and Language Therapists.

"All too often it's seen as something comical or a joke and people will laugh at people who stammer either because they think it's funny or they're embarrassed by it.

"For the person who stammers it is an appalling situation, they know exactly what they want to say but can't say it."

The campaign has high-profile supporters including singer Gareth Gates – who has suffered from a stammer in the past – and politician and shadow cabinet member Ed Balls, who reportedly revealed his stammering problem this year.

He said at the time: "You find ways to deal with it. You cope but it never goes away... you just have to relax and be yourself."

The film and a book by the same name focus on the work of Lionel Logue – a former actor who set up business as a speech therapist in London in 1924 despite having no formal training.

He ended up being welcomed into the heart of the Royal Family as he helped the King gain control over his speech.

But while Logue was hailed as an innovator with his approach – which included breathing and speech exercises – today his therapy techniques and most people's understanding of stammering are outdated.

It's often believed that stammering is caused by shyness, a neglected or difficult childhood or social awkwardness. But, according to experts, it is a neurodevelopmental disorder that seems to emerge in 5 per cent of children aged under five – although only around 1 per cent of adults stammer.

Today's speech therapy may involve relaxation and breathing, cognitive behavioural therapy, and prolonged speech repeating long, drawn-out vowels – either to help a patient manage a stammer or to reduce it.

"We always try to explain stammering to people by saying that people don't stammer because they are stressed about speaking, they are stressed about speaking because they stammer which is a perfectly normal response," says Lieckfeldt.

"The actual audible stammering really is a tip of an iceberg by the time you are an adult. At the top you have around 10 per cent of the physical difficulties of speaking and then gradually over time the hidden negative emotions around speaking – the embarrassment, shame and avoidance tactics – set in and make up the other 90 per cent.

"That's why it's so important for small children with the condition to be given speech and language therapy before the age of five, as it will be most effective before those emotional barriers have built up."

The British Stammering Association's tips:

Speech therapy is available on the NHS and your GP can give you a referral.

If your child starts to stammer, seek a referral to speech therapy to find out if they're likely to recover naturally.

If you're in conversation with someone who stammers, listen to "what" is being said, not "how" it's said, don't finish off sentences or words, try to maintain eye contact and slow down your own rate of speech by using pauses and not rushing replies.

INFORMATION: The British Stammering Association offers help and support to sufferers, visit www.stammering.org; Giving Voice campaign www.givingvoiceuk.org

TRIED & TESTED: The Alexander Technique

Cold weather and festive stress can suddenly make us aware of an aching back or mysterious aches and pains.

Often these can be caused by poor posture or sitting habits – of which we may not even be aware.

Our tester, Claire Spreadbury, checked out a method that aims to get everyone walking tall.

WHAT IS IT? The Alexander Technique is about re-tuning the relationship between your head, neck and back, so you look, feel and function better.

The Technique teaches people about how we move, stay still, breathe, and choose our reactions to situations.

It claims to help alleviate aches and pains, and promote a feeling of mental wellbeing as the body and mind are more in harmony.

It was first developed more than 100 years ago by Frederick Matthias Alexander, an actor struggling with a hoarse voice who taught himself to

correct the balance of tension in his neuromuscular system – so improving his voice and general performance.

WHAT IS IT LIKE?

I went along to an Alexander Technique session with no real knowledge of it and thinking it was something to sort your back out.

It's not a series of treatments or exercises, but rather a re-education of the mind and body, which can be applied to sitting, lying down, standing, walking, lifting, and other daily activities.

Everything about it makes sense – it's about returning to your former self – the natural, flexible posture you enjoyed as a young child before all the bad habits crept in: And mine really have crept in!

The sessions are tough but relaxing. You have to concentrate to try to make your body go like a dead weight, while someone else manoeuvres your limbs.

I can imagine it working wonders if you have the time to put into it – it's certainly not something you'll crack in a few sessions. But from one session alone, I learned that my head should always sit slightly more forward and down than it currently does, which I'm trying to replicate as it's really beneficial.

And I'm endeavouring to correct one of the most common posture faults, sticking my head forward as I sit at a desk to 'lean' into my computer.

There's so much more that could be gained with a full programme of lessons and I'd definitely recommend this technique.

Information: The Alexander Technique is available nationwide. Find a qualified, registered teacher from The Society of Teachers of the Alexander Technique (STAT) by visiting www.stat.org.uk