"If you were to live up to his standards and his ideals and his rules, he should stand down, otherwise it's hypocrisy. I suggest that he's holier than thou and should take a good hard look at himself."
Mr Shearer was also the target of barbs from the Prime Minister when during question time he asked Mr Key if he stood by all of his statements.
"Yes, I do stand by all my statements, and in that I include bank statements," Mr Key said.
Earlier, Mr Key told reporters anybody could make a mistake, including himself.
"When I do, I try and tell people I've made them. It's just that you don't get cut any slack from the Labour Party when you say you've made a mistake, but when they make one they don't want anyone to have a look at it."
Mr Shearer denied he was guilty of a double standard.
"When I myself found that [bank account] error I made the move to correct it, I didn't wait for anybody else to find it."