A report into an SAS exercise which saw a West Country soldier die says it could happen again.
Corporal James Dunsby from Trowbridge died alongside two others after taking part in the exercise in temperatures in excess of 29C.
In March last year The Health and Safety Executive (HSE) issued a Crown Censure following the tragedy on one of the hottest days of 2013. It is the highest level of public condemnation that can be issued.
Now a new report, commissioned by the Ministry of Defence, has said further training exercises still "remain vulnerable" to another incident.
It was undertaken by the independent watchdog, the Defence Safety Agency, which monitors the MoD.
The damning report added that until reservists were given the correct training - and their role fully understood and determined by commanding officers - the risk of death would continue.
An investigation carried out by the HSE shortly after the deaths, found a failure to plan, assess, and manage risks associated with climatic illness during the training.
It was these failings which resulted in the deaths of the Cpl Dunsby, Lance Corporal Edward Maher and Lance Corporal Craig Roberts, and the heat illness suffered by 10 others on the march.
Corporal Dunsby died in hospital from multiple organ failure more than two weeks after collapsing on the march in July 2013.
Lance corporals Edward Maher and Craig Roberts were pronounced dead on the Brecon Beacons after suffering heatstroke.
The MoD says it is doing all it can to prevent any deaths from happening again.