As a lawyer, he has represented powerful bankers and businessmen accused of fraud.
Javier Lozano, Mexico's labour minister, said: "He's a magnificent lawyer. He's a man with a firm hand ... the arrival of Fernando Gomez-Mont should fill us with hope."
Bribery and intimidation
Calderon has made winning the so-called "drug war" a cornerstone of his presidency.
|Rumours have been rife that Mourino's death was caused by the drug cartels [AFP]
Violence involving the army, federal police and rival gangs has killed more than 4,000 people across Mexico this year.
With mid-term congressional elections due in July 2009, Calderon said he had asked Gomez-Mont to work to keep drug gangs from interfering with elections.
Calderon has warned in the past that drug cartels have tried to intimidate and bribe candidates.
Effectively a vice president, Mexico's interior minister is in charge of domestic security but also works with opposition parties to drive the government's agenda in congress.
As an independent lawyer, Gomez-Mont defended high-profile clients such as ex-president Carlos Salinas, a former director of oil monopoly Pemex, and the Canal 40 television network.