I am aware of the presence of fabricated data in a patent application. Whom should I report? What are the consequences to the reporter and the applicant?
In principle that is a form of fraud. Not sure what country you are referring to but different jurisdictions have different procedures.
Here's what the US says: http://www.uspto.gov/web/offices/pac/mpep/s2016.html
Contacting the attorneys of record with PROOF of the fraud obligates them to submit these data to their respective patent offices.
In the USA you may find the attorneys of record at the PAIR public site using the application number or a variety of other document numbers.