"I told him that we are absolutely determined, as I told him a year ago, to hold the consultation," Mas said, a reference to the Nov. 9 referendum.
Rajoy's office later issued a statement noting that he "made (it) clear that the consultation is illegal, that it cannot be held, and that it won't be held."
Spain's parliament and its Constitutional Court, in separate rulings, decreed a self-determination referendum, as Catalonia has planned, is illegal.
Polls show 70 percent of Catalonia's residents favor a referendum, but only about half support breaking away from Spain.
The area, which includes the city of Barcelona, has over 7 million residents, more than Ireland or Norway; its own language and ethnic traditions; and a belief it pays more in taxes to the national government than it receives in services. It also has a long list of grievances against the Spanish government, dating back to the repressive military government of the 1940s that lasted until the 1970s.