Mum Louise Phillips is backing a national campaign to highlight the risk of cardiac deaths in young people after losing her teenage son Jack to an undiagnosed heart condition two years ago.

Jack, who had been discharged from hospital after months of tests for symptoms such as dizziness, fainting and palpitations, attended Royal Wootton Bassett School.

He was just 14 when he collapsed on the street outside a supermarket in Lyneham and, despite the best efforts of an off-duty RAF paramedic and a community first responder, he died on arrival at hospital.

After his death in September 2011 the Phillips family, from Bradenstoke, along with many friends, became involved with the charity Cardiac Risk in the Young (CRY) and more than £19,000 has been raised in his memory. The charity’s new campaign, to be launched today, will highlight the fact that 12 people under the age of 35 die every week in Britain from previously undiagnosed heart conditions.

A postcard featuring a photo of Jack and 11 other young people from across the region who lost their lives will be unveiled by the charity at an event in Gloucester today.

More than 150,000 copies of the postcards have been distributed by CRY families across the UK in a bid to raise awareness and lobby support among MPs.

The charity’s screening programme tests around 12,000 young people across the UK every year and one in every 300 of the young people that CRY tests will be identified with a potentially life-threatening condition.

Mrs Phillips said: “We have joined the postcard campaign to support CRY with the valuable work they do, which includes screening, research and counselling.

“My son Jack was one of the 20 per cent of sufferers that displayed the symptoms of a potentially fatal arrhythmia; however, he was discharged from the local Swindon hospital when initial tests were negative.

“Creating awareness of the potential symptoms is of paramount importance, as is raising money to achieve greater research in this field to ensure that others do not go through the same heartbreak as we and so many other families are having to cope with today.”

Alison Cox, chief executive and founder of CRY, said: “Our campaign is continuing to help us emphasise the importance of screening and the fact so many of these tragic cases affecting fit and healthy young people could have been prevented.

“I’m extremely grateful to the Phillips family for agreeing to lend their support.”