There have been lots of claims along these lines over the years but they've all turned out to be silly in hindsight - e.g. John Williams and his preposterous claim that US GDP has been steadily contracting since 2000, due to an understated deflator.
Granted that any measurement of "inflation" involves lots of guesswork and subjectivity when it comes to hedonic adjustments, but the numbers just can't be dramatically off-base. If they were then weird effects would show up elsewhere, e.g. in productivity figures or corporate earnings, and the USD would also presumably be steadily declining.
All you gotta do is look at the cost increases in the "things" you buy. The REAL inflation rate is closer to 10% than the BS story we get from the government and Fed.