Blake Shelton Ripped Over Prerecorded New Year's Eve Performance

Blake Shelton is being dragged online for his prerecorded New Year's Eve performance ... and some are saying it's an embarrassment to country music.

Here's the deal ... Blake was featured on CBS's "New Year's Eve Live: Nashville's Big Bash" in what was billed as a live show, but folks figured out it was prerecorded and then trashed him.

Blake and Trace Adkins reunited for the CBS show, singing some of their oldies like "Hillbilly Bone" and "Hell Right."

Thing is ... Blake's performance aired only a few minutes before he took the stage in real life at a casino in Oklahoma.

Fans quickly caught on and ripped the network and Blake for double-booking ... firing off some angry tweets.

One user said Blake was "an embarrassment to country music" ... while another said Blake and Trace's duet was "one of the dumbest songs."

Blake's legit live gig went down at Oklahoma's WinStar Casino ... where he performed his hits to much better reviews.

Meanwhile, Blake's wife Gwen Stefani was working too ... she had a gig over in Las Vegas ... and it was live.