Seumas Milne, the Labour party's head of communications, has quit The Guardian, according to an email sent to the newspaper's staff.
"I'm writing to let you know that, following a period of unpaid leave from Guardian News & Media, Seumas Milne has decided to continue in his role as the Labour party's strategy and communications director, and is leaving the staff of the Guardian," wrote Kath Viner, the paper's editor, in a message passed to BuzzFeed News.
"I would like to thank Seumas for his brilliant Guardian journalism, and we hope he'll write for us again in the future."
Milne was originally given a year's unpaid leave in late 2015 to take the job advising the Labour leader. When the 12 months was up he continued in the role, with The Guardian continuing to say he was simply on extended leave.
He had been with the newspaper since 1984 and was a columnist before becoming involved in active politics, playing a central role in the Labour leader's office. There had been doubts over how he could return to the newspaper after being active in politics.
Milne played a key role in organising against last year's Labour coup by centrist MPs. His name was immortalised when a TV camera picked up Jeremy Corbyn whispering "Seumas, I'm not sure this is a good idea" as they staged a photo opportunity featuring the new shadow cabinet.