Strategy of killing gang leaders has led to proliferation of smaller and more dangerous groups, says new attorney general

The fracturing of Mexico's organised crime syndicates by a government-led crackdown on drug cartels has created between 60 and 80 new trafficking gangs, according to the nation's attorney general – far more than were active six years ago.

Speaking on Mexican radio on Tuesday, the attorney general, Jesús Murillo Karam, said former president Felipe Calderón's efforts to stamp out drug trafficking by going after the kingpins had only succeeded in splintering the gangs, spawning many smaller and more dangerous criminal syndicates.

The critique extended an attack by President Enrique Peña Nieto's new government on Calderón's security policy, which focused on killing and capturing the heads of cartels.

Murillo Karam told MVS Radio officials were working to identify all of the country's 60 to 80 small- and medium-sized drug trafficking gangs. In its last public evaluation of the strength of Mexico's cartels, the Calderón administration issued a report in August naming only eight large organisations. It said, however, that at least one cartel – the Beltrán-Leyva group – had split into fragments after a government offensive that killed its leader.

Murillo Karam elaborated on the new administration's criticism of the Calderón strategy, holding it directly responsible for a rise in kidnappings and related crimes over the last six years.

"It led to the seconds-in-command – generally the most violent, the most capable of killing – starting to be empowered and generating their own groups, generating another type of crime, spawning kidnapping, extortion and protection rackets," he said.

The secretary of the interior, Miguel Ángel Osorio Chong, launched the critique of Calderón's strategy by telling a meeting of Mexico's national security council on Monday that while financial resources dedicated to security had more than doubled, crime had increased, and with the capture of dozens of drug capos, cartels had splintered and become more dangerous.

Calderón repeatedly emphasised before leaving office that his forces had captured 25 of Mexico's 37 most-wanted drug lords – a strategy backed by the US government with hundreds of millions in funding and close co-operation with American law enforcement, military and intelligence agencies.

Osorio Chong and Peña Nieto have promised to move away from that focus on leaders and towards reducing crimes against ordinary citizens – most importantly homicides, kidnappings and extortion. Nearly three weeks into their administration, however, they have offered few details on how they will do that.