The Prime Minister does not conduct significant government business via text message or private email, his office says.
A decision on whether John Key's deletion of his text messages amounts to a destruction of the country's public records is progressing.
The investigation by chief archivist Marilyn Little comes as a spotlight is put on politicians' recordkeeping by Hillary Clinton's use of private email for official business. Ms Clinton, a top contender for the 2016 Democratic nomination for US president, last week said that she used private emails out of "convenience" during her time as Secretary of State.