Dr. Shivakumar, Thanks for the citation. However, I have noticed that all the cases are specific to the matter at hand and the circumstances under which the problem occurred. The judgments are therefore to be read deeply to know how much of those conditions apply to the particular case.
Unfortunately, people look at the summary of the judgment and automatically assume the same judgment will be in their own cases. So, I thought I would take the opportunity to reiterate that (as you have pointed out), people must read the judgment carefully to know the circumstances. Second, unless you are diligent in ensuring that the workers are given their dues, the courts will not support you.
If you are careless or in any way collaborating with the contractor in avoiding dues, paying lower, etc., the courts will make you as much liable. Of course, the first recourse is to the contractor and then to the principal employer. But if the contractor fails to pay, they are very much likely to transfer the amount to the PE.