Polio has broken out in Syria. What are we going to do about it? There are refugees starving in the Sahara and drowning off Italy. Shias are being massacred in Iraq, Congolese are being raped, Egyptians tortured, Roma trafficked, Pashtun villagers drone-bombed. You can't stand idly by. Do something.

This week is the 150th anniversary of the forming of the International Committee of the Red Cross (ICRC), in 1863. Four years earlier a Swiss businessman, Henry Dunant, was passing through the Italian village of Castiglione and found it swamped by soldiers from the battle of Solferino. The armies had departed, leaving 40,000 dead and wounded on the battlefield. Dunant desperately rallied the villagers to bring water and dress wounds on both sides. For him the task was straightforward. He had arrived after the event and needed simply to clear up the mess. His principle of impartiality held. Even during two world wars, the red cross symbolised neutrality, humanity's simple protest against the orgy of suffering.

Today that is not so easy. There are hundreds of similar charities round the world, each with overlapping ambitions. I remember a colleague returning from Ethiopia during the 1983-85 famine dismayed at the chaos of the refugee camps, with charity and NGO tents pitched like rival armies across the field of misery. Each craved publicity for fundraising back home. There was no co-ordination.

These things are better organised today by the UN and disaster relief committees. The ICRC has itself sprouted national societies and Red Crescent affiliates. But after the catastrophes in Ethiopia and Yugoslavia a spell was broken. The suffering was seen as politically engendered and complex. These were acts not of God but of men. Why pour aid into Ethiopia when it was either stolen or assisted mass relocation? The charitable prerogative was complicated by politics and diplomacy. Soon it was corrupted by a military embrace. Linda Polman wrote a book, War Games, arguing that aid was furthering war rather than countering it.

Tony Blair's famous (or infamous) Chicago speech of April 1999, instigating the Kosovan war, was trumpeted by him as signalling "the first of a new generation of liberal humanitarian wars". From then on, liberal interventionism was identified not with Red Cross neutrality but with bombs falling and guns blazing "to save little children".

Noam Chomsky pointed to the irony of the emergent concept of "a new military humanism" and to the obscenity of using the least humanitarian weapon, the air-dropped bomb, in its cause. Even Henry Kissinger called Blair's approach "irresponsible", and Bill Clinton's White House complained of Blair having "too much adrenaline on his cornflakes".

A severe toll was inflicted on the Red Cross. Though its work extends to relieving natural disasters and supplementing healthcare, its classic purpose remains impartial relief in time of war, notably where civilians are caught in crossfire. It struggles to sustain an image of neutrality. In Afghanistan this has worked. The Red Crescent has access to prisoners held by the Taliban and trains Taliban first-aid workers, whereas other aid organisations are seen as in collusion with the Nato occupation.

But even the ICRC cannot avoid the taint of association with western interventionism. The attack on its Baghdad headquarters in 2003 suggested its impartiality was no longer universally acknowledged. Red Cross staff have been in killed in Chechnya, Sri Lanka, Congo and Syria and the tempo of such attacks, as on aid workers of all persuasions, has increased.

In 2005 the ICRC commissioned a report on its neutrality which concluded emphatically that "military force … as an instrument for gaining peace is for the Red Cross not applicable". That seems ever more like spitting in the wind. Humanitarian agencies spring up by the week, often in the lucrative baggage train of the military-industrial complex. As a result, foreign intervention in today's "wars among the peoples" risks not just being seen as aiding one side but as actually doing so. This is particularly the case when, as often, western military invasion and occupation have been justified as humanitarian. Like "peacekeeping" of old, the parlance of modern war can be contradictory.

As a result, "doing something" has come to imply something political, if not military. On Thursday the former British foreign secretary and champion of Blair's wars, David Miliband, visited the BBC to promote his International Rescue Committee's efforts to get polio vaccine to Syria. He could not resist confusing humanitarian relief with more partisan intervention. He demanded "a humanitarian ceasefire" in Syria and a "rallying of a sense of outrage and also a determination to do something".

The Red Cross may protest its humanitarian purity, but its mission has been hijacked and compromised by political and military adventurism. How can a British NGO be safely neutral in Syria when Britain's prime minister has called for war against the Damascus government? It is dreadful but perhaps not surprising that doctors are targeted at checkpoints for delivering aid "to the wrong side".

The urge to relieve human suffering is profound, even if it means interfering in another country's affairs. It may seem sanitised by being called intervention, but interference it remains. To be lawful, it must be utterly divorced from politics and diplomacy and, above all, it cannot seem to give moral purchase to war. War has its own logic, its own morality. Charity's business is not to end war but to relieve war's consequences.

Of all Blair's legacies, the most outrageous is the jeering accusation that non-violent humanitarianism is "standing idly by", is doing nothing. Blair's wars undermined Dunant's concept of impartial neutrality. Somehow, the ICRC desperately needs to reassert it.