Images of a terminally ill man ending his own life in a Swiss clinic are to be shown on British television for the first time tonight. The scenes were filmed with the patient's consent. His widow has praised the film for breaking the "taboo" that surrounds assisted suicide.

Craig Ewert, a retired university lecturer and IT specialist, paid the Dignitas clinic £3,000 for an assisted suicide after being crippled by the incurable motor neurone disease.

He agreed to a Canadian film director recording his final moments to "remove the veil" that made people reluctant to think or talk about his death, his widow, Mary, told The Independent. He had told his family years earlier that he would rather die by his own hand than be incapable of looking after himself.

He believed that broadcasting his last moments would be "educative". The film shows Mr Ewert with Mary, his wife of 37 years, at his side, swallowing a lethal mixture of sedatives and switching off his life-support machine. He needed a mouth-operated system to switch off the machine because he had lost the use of his limbs. He died 45 minutes later.

Their final exchange of words begins with Mrs Ewert saying : "Can I give you a kiss?" He replies: "Of course." After they tell one another that they love each other, she says: "Have a safe journey. I will see you some time."

A retired social worker, Arthur Bernard, 63, who has acted as an "escort" in more than 100 assisted suicides for Dignitas, then mixes the sedative and pours it into a glass. He says: "Mr Ewert, if you drink this you are going to die."

The patient drinks the mixture through a pink straw, then asks for apple juice, and for music to be played. Just before he closes his eyes, he says: "Thank you." His wife bids him a good journey and says: "Have a good sleep."

His death is the centrepiece of the film The Suicide Tourist, by an awardwinning Canadian director, John Zaritsky, which has been shown in private screenings in the Netherlands, Canada and the US. The director interviewed Mr Ewert, 59, at his home in Harrogate, Yorkshire, after the Dignitas clinic put them in touch.

The film's producer, Terence McKeown, from the Point Grey Pictures film company in Vancouver, said: "We felt there was a great deal of value in demystifying this suicide process, because whether people approve of it or not, we think they understand it. If people want to attack it, they should at least know what they are attacking."

The decision to screen the film, on Sky Real Lives channel, drew criticism yesterday from people who saw it as an invasion of privacy, and from those who oppose assisted suicide.

John Beyer, the director of the television watchdog Mediawatch-UK, said: "This subject is an important political issue at the moment and my anxieties are that the programme will influence public opinion.

"Documentary-makers produce all manner of programmes and no one can stop that or intervene unless they fail to comply with the requirements of the Communications Act. If this programme is not impartial and promotes euthanasia then it would be in breach of the Act; in short, it must not influence members of the public or a change in the law."

In an implied criticism of the law, Mrs Ewert, who now lives in Chicago, said that her husband might have lived longer if euthanasia was legal in the UK. In England, Wales and Scotland, anyone assisting a suicide is liable to a charge of murder. This has led terminally ill British patients to take their own lives in Switzerland where the laws permits assisted suicide. Dignitas has helped more than 700 people from 25 countries to die since 1999.

Last month, Debbie Purdy, 45, who suffers from multiple sclerosis, lost her landmark legal attempt to clarify British law on assisted suicide. She feared her husband would be prosecuted in Britain if he travelled with her to Switzerland when she took her own life with Dignitas.

Mr Ewert, interviewed for the film at home and in the clinic, said: "I am tired of the disease but I am not tired of living. I still enjoy life enough that I would like to continue but the thing is that I really cannot. If I opt for life then that is choosing to be tortured rather than end this journey and start the next one. I cannot take the risk. Let's face it, when you're completely paralysed and cannot talk how do you let somebody know you are suffering? This could be a complete and utter hell. You can watch only so much of yourself drain away before you look at what is left and say, 'This is an empty shell'. Once I become completely paralysed I am nothing more than a living tomb that takes in nutrients through a tube."

*The parents of Daniel James, the 23-year-old rugby player paralysed in a training ground accident, will not face criminal charges for taking him to Switzerland and helping him to die, the Crown Prosecution Service announced yesterday.

Mark and Julie James admitted that they took their son to the Dignitas clinic to commit suicide in September this year – 18 months after he was diagnosed as a tetraplegic after a rugby tackle left him paralysed from the waist down.

Yesterday, the Crown Prosecution Service decided that "such a prosecution was not in the public interest".

The last moments: How Craig Ewert killed himself

The lethal dose

Craig Ewert is shown drinks a lethal dose of sedatives through a straw. Motor neurone disease has left him paralysed and unable to use his hands.

The final act

Next he switches off his oxygen supply with his teeth. For his death to be counted as a suicide, it is essential he drinks the lethal cocktail and switches off the oxygen himself.

The death

A doctor checks to see if there is a pulse. The doctor may not administer the lethal drugs or switch off the oxygen; he might then be charged with homicide.