Blake is a former congressman from the northern state of Baja California, a border region plagued by drug violence.
Announcing the appointment, Calderon said Blake who had previously been interior minister in the Baja California state government, had "played a fundamental role in confronting in a decisive way the problems of violence in that state."
|More than 26,000 people have died in
Mexico's drug war [EPA]
The president added: "The knowledge he has of crime, and the good relations he managed to build between the police and army in the fight against crime in Baja
California, will without doubt be of great value in strengthening the fight for public safety."
Gomez Mont's departure followed a falling out with Calderon over controversial alliances between the ruling conservative National Action Party (PAN) and left-wing parties in state and gubernatorial elections held on July 4.
In the elections the PAN paired up with the left-wing Party of the Democratic Revolution (PRD), it's archrival in the 2006 presidential race, to wrest control of three governor seats from the resurgent Institutional Revolutionary Party, or PRI.
Popular support for Gomez Mont and Calderon had been dented in recent months by a jump in civilian deaths in Mexico's drug war, which has claimed the lives of more than 26,000 people over the past three-and-a-half years.
The drug war has been the top priority for Calderon, who took office in late 2006, sending thousands of troops and federal police to key smuggling corridors across Mexico.
In a separate development on Wednesday Calderon also said Mexico's economy minister, Gerardo Ruiz, was leaving his post and would be replaced by Bruno Ferrari, who had headed the government agency that promotes Mexico as an investment destination.
Ruiz will now become one of the president's senior advisers, Calderon said.