Ummm, why is your potential new employer calling your current employer? Like what is the reasoning behind that? That is never a good look.
That along with what others have mentioned, this just seems like the complete wrong approach.
I am in a current situation where I signed a contingent offer with a company that is in the same space as me, and is even on many contracts my current company is on. They are having trouble finding a spot for me however due to some contractual obligations as well as me not wanting them to tell my current company that they are shopping me around. This has been going on since March and they have been 100% on the same page as me as far as not letting my current company know.
Additionally, the initial offer was only $10k more than I make now and included less days off. But I told them what it would take for me to switch and they gave me a formal contingent offer letter with $25k more than I make now + the same amount of days off. So it's all in writing and signed by both of us, so there will be no disagreements if/when they find an actual spot to put me on.