ACT leader John Banks is calling Labour leader David Shearer a "rampant hypocrite" and wants him to quit after failing to declare his US bank account with $50,000 in it.
Mr Shearer made the revelation yesterday, saying he simply forgot to add it to his pecuniary interests list when he became an MP.
He has now declared it to Parliament, but Mr Banks says it is not good enough and wants him to "fall on his sword".
"Mr Shearer is on record last July as saying 'anyone with a memory lapse is not fit for public office and should stand down'.
"He has had a memory lapse and if you live up to his standards and his ideals and his rules, he should stand down. Otherwise, it's hypocrisy," says Mr Banks.
In July last year, Mr Shearer heavily criticised Mr Banks for failing to declare a gift basket he received during his Auckland mayoralty campaign.
Mr Banks says it is a double standard and Mr Shearer needs to practice what he's been preaching.
"He's being a hypocrite because there's one rule for David Shearer and another rule for the rest of us. He needs to do the right thing and fall on his sword today."
Mr Shearer says the two declaration failures are incomparable because he discovered his own mistake and came forward whereas Mr Banks didn't.
"I didn't wait for anyone else to declare it, I did it myself," he says.