Governments are doing far too little to clear up unexploded bombs and leftover landmines, while some even continue to manufacture and stockpile the weapon.
Six years after the entry into force of the Ottawa Convention banning anti-personnel mines, forgotten mines remain a serious problem across the world, according to an international report.
The study was produced by Landmine Action on Sunday, the British arm of the International Campaign to Ban Landmines.
"Explosive remnants of war are costing civilian lives and livelihoods in 90 countries, many of them the world's poorest," said director Richard Lloyd.
Landmine Action said not only were children being killed and maimed as they unwittingly played with the brightly coloured unexploded bomblets from cluster bombs, but land and anti-tank mines were slowing post-war aid delivery.
More than 140 countries have ratified the Ottawa Convention that commits them to immediately stop production and use of landmines, destroy their stockpiles and clear their territories of them within a decade.
Most are way behind schedule. But more than 42 others - notably the US, Russia, India, Pakistan and China - have refused even to sign and still hold vast reserves of landmines.
Lloyd said his survey was the first to methodically take a country-by-country and weapon-by-weapon inventory of the problem and showed that the scale of it had been vastly underrated in the past.
"It is a massive problem that is simply not being adequately tackled by most countries," he said. "Many governments have to put far more resources than they currently are into dealing with this."
At least 20,000 people a year are killed or maimed by previously unexploded munitions - mostly men and children - and it is worst in Afghanistan, Angola, Bosnia, Cambodia, Eritrea, Iraq, Laos, Somalia, Sri Lanka and Sudan.
Landmines, in contrast to other munitions, are designed to maim and incapacitate rather than kill.
This is based on the understanding that while a dead person needs no further action, a maimed one involves many others in transport and caring and is a major drain on the resources of the enemy against whom they are directed.