Appreciate your effort to inform your HR timely. However, before proceeding, I would want to understand that your doubt is based on facts which will remain unchallenged no matter how deeply it is examined.
Understanding Your Role
Hence, please allow me to begin by asking your role in the team. Are you the reporting manager to the new hire? If not, are you a team member, and how is your team structured? What is the role in which this person is hired? A little background on your role would help us guide you correctly.
Evaluating the New Hire's Experience
About your doubt regarding the experience claimed by the new hire, how did you detect his or her incompetence? From your statement, it sounds as if the new hire has the education in place but not the practical experience. How did you arrive at this conclusion? Is your doubt based on a factual incident where work was allocated to the new hire and he or she couldn't deliver? Are you sure there was a conducive environment for performance? How close is the skill required to deliver the job compared to what any other new hire may have? Have you tested this person on the basic skills? At times, basic skills differ from those required in the delivery phase. For example, a programmer may know a computing language very well. However, developing a product could still remain light years away. Product knowledge often requires many more addendums on the threshold skills.
Considering the Learning Curve
Given the fact that every new hire will bring his or her own learning curve, did you take that into account? Are you sure the learning support is in place to bring a new hire up to speed? Every answer to these questions will help build your case stronger.
Handling Fraudulence Claims
Please keep in mind that the new hire has gone through the same interview procedure that every other employee working in the role went through. Hence, the opportunity for error would be minimal. When you claim fraudulence, please be assured that you might ruffle a lot of feathers. The new hire might not be anyone's favorite, but proving a gap in the hiring system might backfire. Therefore, please pre-wire that first. Talk to your superiors to understand how such cases were handled earlier.
Maintaining Professionalism
Your effort to save your team from a bad hire must not be misconstrued. Hence, make sure you are rightly understood by your reporting managers. Please keep none of your personal agendas around it. In no case should you try to get any limelight or credit out of this situation. Stay focused on serving your organization and none of your personal gains.
Raising a red flag during the probationary period would help your team. Wishing you all the best in your effort to save your firm!