Lerner has spent more than £250million in six-and-a-half years at Villa including £23million on new signings last summer.
There will be no spending along those lines during the current transfer window but Lambert was aware of the need to work within certain financial parameters when he replaced Alex McLeish.
Paul Lambert: "You can't spend something if it's not there. I think he has got money, or his own wealth, entirely his own wealth.
"I think what's happened is the club spent millions a couple of years back. It can't do that, there's absolutely no way it can do that.
"Finance dictates a lot of things. Finance will always dictate a lot of things.
"The one thing is he's not washed his hands of [the club].
"Anyone who puts that level of money in over the years.it's been an incredible amount of money.
"I think people are looking for things because he doesn't come [to all the games].
"If he has got other commitments, that's entirely up to himself, if he has got other things on. But he's definitely behind the club. He wouldn't have done what he's done if he wasn't committed to it."
Randy Lerner: "In the time that I've come to know Paul, what is clear above all else is his strength of character and belief in his approach to football.
"I would reiterate that Paul has achieved success at many levels of professional football and I believe, given support, he will continue to do so for us."
"Fortunes can shift quickly in this game and a sense that one has it right can become grave doubt in a matter of a few games.
"The Villa board knew that with Paul we would begin to address the club's multi-year lack of competitive stability by reshaping the squad with seven new signings in the summer.
"It has been rewarding at times this season although certainly frustrating as well, particularly recently."
Source: Newcastle United Mad