Ed Miliband's backing for a permanent 50p tax rate for high earners was made "in the cut and thrust" of Labour's leadership election and could be dumped as a policy, Alan Johnson said.
The shadow chancellor - who said this weekend he was against keeping the higher rate - said there were a number of prior disagreements within the shadow cabinet that needed "working through".
Mr Johnson said it was a "mark of the man" that the new Labour leader had been prepared to appoint people such as him to key posts despite differences of opinion on some issues.
During the fight to succeed Gordon Brown, Mr Miliband said the 50p rate should stay in place, saying it was "not just about reducing the deficit, it's about fairness in our society".
Asked about the measure's future yesterday however, Mr Johnson told The Times it was not ideal and that he backed it only "for the times we are in".
Quizzed on the difference of views, he told BBC1's Politics Show: "You have to separate what is going on in a leadership contest, where people say all kinds of things in terms of the cut and thrust of that campaign, with where we stand now.
"Ed was asked for his opinion during the election campaign and he gave it, I was asked for my opinion yesterday.
"In terms of a new shadow cabinet coming together with a new leader, we will sort these policies out and get to a position. We have not worked out every dot and comma on every issue.
"We didn't introduce the 50p tax rate five years ago and we might not see the need for a 50p tax rate in five years' time."
Mr Johnson said there had been a "very big difference" of opinion over the merits of a graduate tax to fund universities which he strongly opposed.
