President says legalistation would undermine fight against traffickers, but others say it would cut corruption and violence

California's referendum on legalising cannabis has divided Mexico into those who consider it a potentially catastrophic betrayal and those who think it could signpost a way out from the horrors of the drug war.

The president, Felipe Calderón, has led criticism of Proposition 19 as a dangerous experiment that would undermine US and Mexican efforts against ruthless and powerful narco-traffickers. The conservative leader and other establishment figures have accused the US of hypocrisy in pressuring Latin America to confront drug traffickers, often at grisly cost, while doing little to rein in the US consumption that drives the trade.

Some fear California's example will blow across the border and boost consumption in Mexico, where drug education and rehabilitation programmes are feeble. "It would be the worst thing. It might cut the cartels' income a bit but we'd see more addicts, and trust me we've already got enough," General Carlos Villa, a police chief in Torreón, told the Guardian.

Cannabis accounts for an estimated half of cartels' income but some studies suggest legalisation in California, which produces its own weed, would barely dent profits and that narcos could in any case expand other operations.

However, a small but growing number of dissenting voices in Mexico, including two former presidents and reportedly four putative presidents, have endorsed legalisation as a way to hit the cartels, reduce corruption and stamp down drug-related violence which has claimed almost 30,000 lives in four years.

If California votes yes, Mexico's government will come under pressure to follow suit, a former foreign minister, Jorge Castañeda, told Nexus magazine. "It is going to be impossible to ask Mexican society to put up with the number of lives at risk and the violence for a fight that Americans, or at least Californians, would have said they don't want to fight any more," he said.