Good work Kiran, and I'd agree "to" is more common in this usage. However I have a thing about unnecessary or redundant words
1. I confided my secret to a friend, but he let it slip and now everyone knows it.
As Im says, the second one is probably okay. However I'm not at all familiar with that usage but more often hear "let on " meaning to act deceptively or give a false impression, as "He let on that he had a college degree"