David Shearer says the point-scoring and "pettiness" of politics was boring and beneath him.
The former Labour leader made the comments on TVNZ's Q+A this morning as a new poll put David Cunliffe at the front of the party's leadership race.
Mr Shearer said he was relieved and disappointed to give up the leadership last month, but he also acknowledged it had been difficult and frustrating.
"The thing I found most difficult really was the pettiness of politics and being in opposition. A lot of it was petty, a lot of it was venal," he said.
"Politicians from all sides come in to make difference, to actually get something done. And what you get caught up with, particularly as a leader, is point-scoring and that sort of pettiness.
"I just found it boring, I found it beneath me and I wasn't very good at it because of that. Other people thrive on it, they love it, I mean that's the thing they love about the arena of politics. To me, I found it below me."
Mr Shearer compared politics with his experience in conflict zones.
"I always felt, oddly enough, more comfortable in war zones than I did not so much in the Labour party, but in politics.
"I mean obviously in politics you're getting sniped at from all directions. In a war zone, you can generally tell who the good guys are and who are the bad guys."
He said the most frustrating thing was getting within two points in the polls of being able to take out National at an election.
Asked why he stepped aside, Mr Shearer said it could have been a "messy, drawn-out affair" and it was cleaner to do it that way.
"I wasn't prepared to go around on a bended knee to my caucus colleagues and ask for their support - it's just not the way I do things."
Mr Shearer said he would "absolutely" stay in politics.
"I'd like to play a positive role, a senior role, in whatever comes up and if I can do that, that will certainly satisfy me," he said.
"You don't get into politics to sit on the back benches and twiddle your thumbs."
He would not say which Labour leadership candidate he supported, but said the party had to get behind whoever won.
"We can't do anything else because if we don't do that, then we won't win. It's as simple as that. The most corrosive issue for us in the Labour party has been disunity."
Meanwhile, a Q+A Colmar Brunton poll of 510 people found Mr Cunliffe was the preferred Labour leadership candidate.
Asked which candidate was most likely to beat Prime Minister John Key in next year's election, 39 per cent said Mr Cunliffe, 18 per cent said Shane Jones and 15 per cent said Grant Robertson.
A further 10 per cent said none and 18 per cent did not know.
As for the candidate most likely to beat Mr Key in a television debate, 36 per cent said Mr Cunliffe, 27 per cent said Mr Jones and 11 per cent said Mr Robertson.
Twelve per cent said none and 14 per cent did not know.
But Mr Cunliffe was just beaten by Mr Jones as the candidate best able to identify with the average New Zealand voter, with Mr Jones on 31 per cent and Mr Cunliffe on 29 per cent.
Mr Robertson was on 19 per cent, while 5 per cent of respondents said none and 17 per cent did not know.