Speaking on TVNZ's Breakfast programme today, Mr Key said the "ugly" tone of the 2014 general election campaign was the low point of his year.
"It was all kind of hate stuff...the whole thing was just awful."
Nick Hager's Dirty Politics book, which covered issues including collusion between Mr Key's former staffer Jason Ede and right-wing bloggers, was a talking point during the campaign.
The Prime Minister's relationship with one blogger raised questions in the public arena and in Parliament, with Mr Key at times forced on the defensive this year.
This morning, the Prime Minister said he no longer responded to texts from blogger Cameron Slater.
"I don't have a terribly great relationship with the guy now. I don't text him if he texts me," Mr Key said.
"Even if I deleted his phone off the system it wouldn't stop him sending me a text. He knows my number. A lot of people do," Mr Key said. "I'm on my fourth mobile phone number as Prime Minister. And mark my words, you'd be amazed who gets my number."
Mr Key also discussed future political roles for embattled former ministers Judith Collins and Maurice Williamson.
He suggested Ms Collins was more likely to return to Cabinet next year than Mr Williamson.
"Maurice is getting near the end of his career...I think he'd like to do other things."
Mr Key said he was heading to Los Angeles and then Hawaii for the Christmas holidays.
NZME.
