The union president representing 12,000 immigration service agents said Monday he is staunchly opposed to President Obama using executive action to allow millions more illegal immigrants to obtain green cards and work permits.

Kenneth Palinkas, president of the National Citizenship and Immigration Service adjudicators and personnel, called reports about planned executive action “dangerous” and said it would increase “exponentially” the health risks, threats to national security and expense to taxpayers that he said are on the rise because of lax enforcement of immigration laws.