You can.. however you need to ask yourself if that is sufficient. The fact that you are asking says it is not.
I might consider using the phase 1 report if the phase 1 company was reputable and I had recourse with them if something turned up later. I've done due diligence on a few parks and was on site when the plumber was doing his inspection. This allowed me to ask questions while he was scoping the lines and we saw things that were questionable.