Farmers say spraying kills all crops and ruins their livelihood

The administrative tribunal of Cundinamarca ruled that spraying of coca crops must be stopped until a study is conducted to determine the effects of the chemicals on the environment and public health.

The programme is the backbone of the anti-drug war in Colombia, and the hardline government of President Alvaro Uribe had vowed to spray more drug crops than ever over the course of this year.

Government officials said they would appeal against the ruling and continue with the spraying in the meantime.

"We respect the ruling but we don't agree with it," said Agriculture Minister Carlos Gustavo Cano.

Agent Orange's cousin

The chemical cocktail glyphosate sprayed from planes on coca crops, the raw material for cocaine, has been dogged with controversy.

Coca farming is a way of life for many Colombians

It is a cousin of the defoliant Agent Orange used by the US in Vietnam.

It has become the cornerstone of the US-Colombian fight against drug cultivation that produces more than 600 tons of cocaine every year - most of which washes up on American shores.

Peasant farmers have long complained that the chemicals kill all crops and ruin their livelihoods, leaving many no option except to join the warring factions or cut down more virgin Amazonian forest to sow more drugs.

But President Uribe had said it was essential to undermine the finances of the warring factions that between them earn up to $1bn every year from the drugs trade.