MEXICO CITY (AP) -- Former Mexican President Felipe Calderon said Monday that the spying the U.S. reportedly did on his presidential email system was an affront to Mexican institutions that should be addressed by current Mexico authorities.
"This is an insult to the country's institutions, more than to a person, since this was done when I was president of the republic," Calderon wrote in a tweet.
Calderon said in another tweet that he will closely follow the efforts by Mexico's Foreign Relations Department to get an explanation from the United States.
A report Sunday by the German news magazine Der Spiegel said documents from National Security Agency leaker Edward Snowden indicate the U.S. gained access to Calderon's email system when he was in office.
Mexico's government said Sunday that it "categorically condemns" email spying. Opposition politicians called that response lukewarm.
Earlier, a document dated June 2012 indicated the NSA had read current Mexican President Enrique Pena Nieto's emails before he was elected.
The U.S. Embassy in Mexico said in an email statement that it wouldn't comment on the spying allegations.
"We are not going to comment publicly on every specific alleged intelligence activity, and as a matter of policy we have made clear that the United States gathers foreign intelligence of the type gathered by all nations," it said.