Mail on Sunday executives are standing behind the newspaper’s extensive serialisation of the memoirs of an ex-mayor of Doncaster, which claimed to give “a worrying glimpse of the real Ed [Miliband]”.

In a front-page story and across five pages inside, the newspaper published what it billed as a series of “bombshell” claims by Martin Winter, a one-time friend of the Labour leader who fell out with the party after leaving office in 2009.

Under the headline My 9½ weeks of Calamity Ed, the serialisation recounts stories about how “bumbling oddball” Miliband accidentally set fire to a carpet and bought a prayer mat to cover the damage, and privately “agonised about his better looking brother David”.

Winter, who helped Miliband to win the Doncaster North seat in May 2005, wrote that his 10-year-old daughter gave his former ally a lesson in economics and how Miliband nearly missed a meeting with Gordon Brown by locking himself in a house.

However, the most politically toxic claim was that Miliband and Ed Balls knew about the economic crash of 2008 a year before it happened but kept it a secret.

A spokesman for Miliband said: “This report is untrue. It is tittle-tattle, a third-hand report of a conversation more than seven years ago. Complete nonsense. No one had any sense of the scale of the global banking crisis which emerged in 2008.”

A spokesman for the shadow chancellor also denied the claim made by Winter, who resigned as Doncaster mayor in March 2009 after Balls, then children’s secretary, ordered the council to bring in a new management team after the deaths of seven children in the area.

Labour figures pointed out that Winter was lambasted in the Mail on Sunday in 2009 in a piece on Doncaster, a town described by the paper at the time as “the rotten borough they call the Haringey of the north”.

But senior Mail on Sunday insiders stood by the serialisation. “It’s good stuff, entertaining,” said one executive, conceding that it was “quite conceivable” people may never have heard of Winter.

“He may be obscure but Ed Miliband isn’t. [Winter] is not a famous person himself but he happened to have interesting periods with someone who went on to be famous.”

In a leader column, the Mail on Sunday said Miliband’s “accident-prone and clumsy bumbling, his awkwardness with children and poorly chosen gifts are exactly what one might expect from a Hampstead intellectual suddenly confronted with the outside world”.

It added: “Of course, we are all human, and there are worse failings. But Mr Winter’s central revelation is much worse. It is not just that Mr Miliband burned a hole in his host’s carpet. It is that he might burn a hole in the nation’s future.”

Calls to Winter for a response went unanswered on Sunday. The Mail on Sunday said his memoirs, titled Fallout: By Martin Winter, The Man Who Made Ed Miliband An MP, go on sale in April.

John Wellington, the Mail on Sunday managing editor, declined to confirm whether Winter was paid for the serialisation: “Anything like that would be confidential. We don’t discuss payments.”

Damian McBride, who was special advisor to then-prime minister Gordon Brown at the time, rubbished Winter’s claim that Miliband and Balls knew about the economic crash a year before it happened but kept it secret. “In all the countless conversations about whether to call an election in 2007, not once did the prospects of the economy come up. Not once,” he said on Twitter.