CitizenAID has been developed by top army doctors to teach people with no medical knowledge to treat victims injured by bomb blasts, gunfire or mass stabbings.
The current terrorism threat level in the UK is 'Severe', meaning an attack is highly likely. The National Counter Terrorism Security Office has already released its Run, Hide, Tell advice for victims caught up in terror-related incidents.
The idea is for members of the public to treat each other in the immediate aftermath of an attack, when emergency services may still be trying to contain the threat and secure the area.
One of the key techniques featured on the app is the tourniquet, a battlefield treatment which can stem heavy bleeding. Medics have expressed concern that although trained workplace first aiders may be able to treat illnesses such as seizures, they will not have been taught how to deal with emergencies more commonly found in combat zones.
The University of Birmingham's professor of clinical traumatology Sir Keith Porter, who has helped to design the app, told the BBC:
"I have treated hundreds of soldiers whose lives have been saved by simply the applications of tourniquets when they have been shot or blown up. Teaching individual soldiers these skills has saved lives.
"And I think it is essential we train the public in those skills and that is exactly what CitizenAID does."
Senior army officer Brigadier Tim Hodgetts is one of the founders of the app.
"We are empowering the public," he told the BBC.
''By giving them a step-by-step system we take away the anxiety because the decisions are already made and the right decisions in the right order can save lives."
The free app is available via Google Play or the Apple Store. A pocket book version can be purchased for Â£1.99 from medtree.co.uk and spservices.co.uk.