Former defence secretary John Hutton has said he did not know there was a plot to try to force Gordon Brown out of Downing St last June.
In a wide-ranging interview with The House Magazine, Hutton said he "wasn't aware" of any plot against the prime minister.
Several members of the Cabinet, including Hutton, left the government in June.
James Purnell resigned and called on Brown to leave office. Jacqui Smith, Geoff Hoon, Hazel Blears and Caroline Flint also stood down.
Flint accused the prime minister of treating the female ministers as "window dressing".
It was widely reported there was a co-ordinated attempt to push Brown out, but Hutton made clear in his resignation statement that he backed the prime minister.
"No-one ever spoke to me about it (the plot), and if they had done I would have told them to grow up and get a grip," Hutton told The House Magazine, which will be out on Monday.
"We've chosen our leader and it's our job to support him.
"However difficult it is, and it is extremely difficult at the moment, we should always stick together and support each other.
"Sadly, the Labour Party doesn't always do that."
Hutton, who is standing down at the general election after 18 years as MP for Barrow and Furness, also warned against the party becoming "more left-wing and true to its socialist origins" in order to win the next election.
"That's how we'd lose it," he said.
"If we lose then you'll hear people on the Left say we lost because we were New Labour.
"That's complete rubbish too. We'll lose if people don't think we're New Labour any more.
"People are not supporting the Tories because we're not left-wing enough. All this stuff about scrapping Trident and setting up a high-pay commission is a complete irrelevance.
"It's the kneejerk politics associated with the Left.
"You won’t find answers to today's problems by flicking through the mouldy old socialist textbooks of the 1920s."
Hutton also revealed that he is not interested in a seat in the House of Lords and he intends to "write more about the First World War" when he leaves Parliament.
Also in next week's issue of The House Magazine, Sam Macrory celebrates ten years of Westminster Hall debates, Michael Gove shares his Commons Diary, BBC deputy director general Mark Byford sings the praises of the corporation's new Democracy Live service and Paul Seaward explores the origins of MPs' remuneration.
