The committee had cited the “disproportionate” cost to the party of a mayoral election to replace Burnham when it blocked his bid to stand in the Greater Manchester seat.
Powell was the only member of the NEC to vote in favour of Burnham.
But she told Newscast she accepted “collective responsibility” for the decision because of the mayoral by-election concern.
Powell said if Burnham had been allowed to stand then “I think certainly the Greens wouldn’t have gone after the seat in the same way that they did”.
Now she said the party needs to look at why Burnham is so popular in Greater Manchester, saying people “see in him someone who is on their side, someone who is delivering those Labour values and those Labour policies”.
“We have to draw on that, make use of Andy Burnham, but also… reflect on how we could do that better nationally and better as a government,” she said.
“And I know from talking to Keir many, many times over recent weeks, before this by-election and since, that that is something he is very focused on doing.”
