Updated 3:03pm: The Greens want to know if the Prime Minister has been following the rules when it comes to his text messages.

They're asking the Chief Archivist to see if the Mr Key has broken public record laws following admissions made in Parliament that he deletes his texts.

MP James Shaw says the texts aren't his to delete and are public records.

"Areas of ministerial responsibility or communications that are in the domain of ministerial responsibility ought to be held on to and I think what we've seen this week is some kind of slipperiness in terms of what the interpretation of what that is."

A spokesperson from Mr Key's Office says the Prime Minister does not conduct substantive ministerial business by text message.