Villa's top-flight status is in doubt after a winless run of six matches, of which five have been losses.
As a result, they have dropped to 16th in the table and sit just three points above the relegation zone with as many games remaining.
And under-fire manager Lambert feels Villa must look to sign proven quality rather than relying on young prospects again next season.
"This club needs big players," he said on Thursday.
"It's not acceptable for this club to keep doing this. Four years it's been battling against it."
Chairman Randy Lerner is rumoured to be interested in selling the club, after originally taking over in 2006 from Doug Ellis.
Lambert feels the success of the American's tenure at Villa Park can not be questioned but says the club are punching well below their weight in the Premier League.
"The chairman will come out and say something in May. I don't know what he's going to say," Lambert added.
"It's his football club, no one can be critical of what he's done for this football club.
"I'm not breaking ranks, I'm just saying the size of this football club needs to be up there. He's been fair with everyone and he will do when the time is right.
"The conversations I've had with him are always really good.
"It's nothing negative but this club can't keep doing what it's doing."
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