The ex-foreign secretary, defeated by his brother Ed Miliband for the Labour leadership in 2010, said a comeback had “not been decided yet”.
The senior figure – who quit as an MP in 2013 – refused to rule out the idea of returning to the Commons when pushed on the matter by LBC presenter Andrew Marr.
“That’s not been decided yet. That’s not done,” said Mr Miliband, after he was asked if he could stand at the next general election.
He said: “I’m not even going to go there, because I’ve got to do justice to the people who are working for the International Rescue Committee ... It means a lot to me that job, and I’m very committed to it.”
Mr Miliband, who remains president and chief executive of the IRC, added: “If you start thinking about your next job, you get yourself into trouble.”
The former cabinet minister also said he was “enthusiastic” about Labour’s direction under Sir Keir Starmer.
“The Labour Party has, thank God, put itself into a position where it’s got good people leading it – it’s developing its plans for government,” he said. “That’s something that I think is really essential for the country that I really care about.”
Mr Miliband declined to criticise Sir Keir’s approach to Brexit, after the Labour leader vowed not to cross the “red line” of bringing back freedom of movement with the EU, and ruled out any return to the single market and customs union.
“In respect of Europe, it seems to me what he’s trying to do is make sure he doesn’t get cornered by his political opponents, which is completely understandable,” said Mr Miliband.
But the ex-Tony Blair policy chief said Britain’s reputation had been “shredded” and called for closer ties with the EU, adding: “We’ve lost European cooperation because of Brexit – we’ve got to build it back.”
Labour sources have said there was no immediate prospect of Mr Miliband being selected as a candidate for the next election, according to reports.
The former New Labour cabinet minister declined to serve in his brother’s shadow cabinet, and later criticised Jeremy Corbyn’s leadership of the Labour Party.
Earlier this week Tony Blair Institute called on Rishi Sunak to “revisit” the Brexit trade deal already agreed with the EU as part of an effort to forge closer economic ties with the bloc.