Mana Party leader Hone Harawira says the Prime Minister has been petty and nasty for suggesting that he is an often absent MP.
John Key on Tuesday morning accused Mr Harawira of what he called taking the mickey by rarely turning up to Parliament.
MPs will have their attendance at debates and select committees recorded and made public from Tuesday. Tougher financial penalties have also been introduced for those who are absent without good reason.
Mr Key says obviously some MPs have legitimate reasons to be away, but most backbenchers should be in the House when it is sitting and some like Mr Harawira need to be held to account.
Hone Harawira has taken 68 days leave during this term of Parliament - all of it approved by the Speaker. He says he is required to travel all over his Te Tai Tokerau electorate.
"My electorate is more than 10 times bigger than Peter Dunne's and John Banks' combined. I am required to travel to many different parts of the electorate - I simply can't do it all in one week.
"I'm also the leader of the Mana Movement and I'm called upon to attend meetings up and down the country and overseas - the majority of which I have to turn down simply because I don't have the time to do them all."
Mr Harawira believes he is one of the hardest working MPs.
The National Party has refused to release its own members' attendance records.