Labour leader Andrew Little says Prime Minister John Key has an "unhealthy relationship" with Whaleoil blogger Cameron Slater.

Mr Slater has been in the thick of National Party ructions either side of the election. He was a key player in Judith Collins resignation as Justice Minister, while his communications with Mr Key last week forced the Prime Minister into an embarrassing backtrack in Parliament.

Speaking on TV ONE's Breakfast this morning, Mr Little questioned Mr Key's judgement in not ending the relationship.

"Cameron Slater is a difficult personality, I think it's probably not too fine a point to say he's a sociopath," Mr Little said.

"He's not a person any responsible politician should be associated with, but the Prime Minister seems to have this unhealthy relationship."

Mr Key told reporters last week he hadn't spoken to Mr Slater on the phone for months but acknowledged Mr Slater "sent me a text one time, I can't remember when that was".

However, it has since emerged Mr Key had a text conversation with Mr Slater two evenings earlier, forcing Mr Key to return to Parliament to correct a statement he had made earlier that he hadn't been in communication with Mr Slater about the spy watchdog's report on the Dirty Politics scandal.

"I think the reason the Prime Minister has to keep him sweet is because there's exchanges they've made which have been critical about the Prime Minister's own Cabinet and other colleagues that he's desperate not to get out into the public," says Mr Little.