David Miliband has called on Labour leader Jeremy Corbyn to fight "future battles and not the past battles" because "every country needs a strong opposition".
The former foreign secretary, who narrowly lost out to his brother in Labour's 2010 leadership election, told BuzzFeed News that it's "really, really important" for opposition parties to avoid revisiting old disputes.
"Every country needs a strong opposition and the big questions facing the UK, including about Europe, about Scotland, are demanding of the attention of people who've got their eye fixed on the future," he said.
"The most important thing in politics is always to fight the future battles and not the past battles."
Asked what specific advice he would give to the new Labour leader, Miliband said he had to be "slightly careful" due to his role as chief of the non-partisan International Rescue Committee charity but referred back to comments he made during this summer's Labour leadership campaign.
In August he used an opinion piece in the Guardian to make a rare intervention in British politics. In it he endorsed Labour leadership candidate Liz Kendall with a warning that "the Corbyn programme looks backwards", suggesting he could turn the party into a "pressure group shouting from the sidelines at a Conservative government".
Miliband, a close ally of Tony Blair, wrote at the time: "The pledges of nationalisation, 7p in the pound increases in national insurance for those earning more than £50,000, and equivocation about Britain's place in the EU are the same ideas that I learned were wrong when I joined the Labour party in 1981."
Although he is often linked to a return to UK politics, Miliband stepped down as an MP in 2012 and currently lives in New York. In a joint interview with former US secretary of state Madeleine Albright he also urged Britain to take in more people fleeing Syria and said the UK should join in on an EU-wide scheme offering homes to refugees: "One of the reasons the EU was created was to cooperate with these kinds of issues, and in my perspective the UK should be part of that."
Jim Waterson is a politics editor for BuzzFeed News and is based in London.
Contact Jim Waterson at firstname.lastname@example.org.
Hayes Brown is a world news editor and reporter for BuzzFeed News and is based in New York.
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