The rumours concerning Lerner were strongly denied by Villa chief executive Paul Faulkner, who insisted the 51-year-old has no immediate plans to walk away.
While Villa have worked on a tighter budget in the past two seasons, Lerner has invested heavily in the playing squad since his 2006 takeover.
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"Anybody who decides to have a shot at him (Lerner) or criticises him is way off the mark," Lambert said.
"He is a private guy, which he is totally entitled to be, and you have to respect that.
"There's no great issue for the fans if Randy is here or not here, and with what he has done.
"If you look at all the facts, the money he has put in and what he has done for the local community, let alone anything else, he is entitled to his way of doing things and you have to respect that."
Lambert also believes he would be aware if Lerner was looking to sell, due to the close relationship between the two.
He added: "It's well documented I'm always in contact with Randy and he's never spoken about anything like that whatsoever, we speak about football.
"I'm pretty sure I'd be one of the first to know.
"But he's every right to decide what he wants to do. He is the main person at this club. But as I've said before, nobody should ever criticise Randy for what he has done at this club."