Paul Manafort indirectly advised Donald Trump’s 2020 campaign while in home confinement as part of a seven-year sentence for offenses including tax fraud – advice he kept secret as he hoped for a presidential pardon.

“I didn’t want anything to get in the way of the president’s re-election or, importantly, a potential pardon,” Trump’s 2016 campaign manager writes in his new book.

In May 2020, as Covid-19 ravaged the prison system, Manafort was released to home confinement. He stayed in an apartment in northern Virginia. From there, he re-established contact with Trumpworld.

“There was no contact with anyone in the Trump orbit when I was in prison,” he writes. “And I didn’t want any, especially if it could be exploited by the MSM [Mainstream Media, a derogatory term in rightwing circles].

“But when the re-election campaign started kicking off, I was interacting, unofficially, with friends of mine who were very involved. It was killing me not to be there, but I was advising indirectly from my condo.”

The startling admission is spelled out in Political Prisoner: Persecuted, Prosecuted, but Not Silenced, a memoir that will be published in the US next month. The Guardian obtained a copy.

Throughout the book, Manafort, 73, strenuously denies collusion with Russia and ridicules investigations by the special counsel, Robert Mueller, Congress and the US intelligence community.

But in Virginia in August 2018, in a case arising from Mueller’s investigation of Russian election interference and links between Trump and Moscow, Manafort was found guilty on eight counts: five of tax fraud, two of bank fraud and one of failure to report a foreign bank account.

In March 2019, he was sentenced to 43 months in prison. Later that month, in Washington DC, Manafort was sentenced to an additional three-and-a-half-year term, having pleaded guilty to conspiracy including money laundering and unregistered lobbying and a count related to witness tampering.

Manafort was also found to have violated an agreement with Mueller, by lying.

In his memoir, Manafort describes his travels through the US prison system – including a stay in a Manhattan facility alongside the financier and sex offender Jeffrey Epstein and the Mexican drug baron Joaquín “El Chapo” Guzmán.

In another startling passage, Manafort writes that during one transfer between facilities, at a private airfield “somewhere in Ohio”, the sight of “prisoners … being herded in long lines and then separated into other buses and on to … transport planes … reminded me of movies about the Holocaust”.

Manafort ran Trump’s campaign between May and August 2016, when he resigned shortly after the arrival of Steve Bannon as campaign chairman and amid a scandal over alleged evidence of payments connected with consulting work in Ukraine.

In his book, Manafort denies wrongdoing in connection with the so-called “black ledger” but writes: “My resignation only deflected attention from the Russian collusion story for a short period of time.”

Describing his informal advice to the Trump campaign in 2020, after four years of scandal, trial and imprisonment, he writes: “I didn’t have any prohibition against it, but I didn’t want it to become an issue.”

He continues: “I still had no promise of a pardon, but I had an expectation. My fear was that if I got in the way of the campaign and Trump lost, he might blame me, and I did not want that to happen.”

Trump lost to Joe Biden – an outcome Manafort, whose career in politics began as an adviser to President Gerald Ford, puts down to Biden’s campaign understanding Trump’s limitations better than Hillary Clinton.

But he also flirts with Trump’s lie about electoral fraud being the cause of his defeat, writing: “I believed there were patterns that were irregular. The results in battleground states were close enough that the fraud could be the difference between winning and losing.”

After Trump lost, Manafort writes, he held off “making phone calls the day after to start working for a pardon” and instead waited on Trump.

Manafort says the news he would be pardoned came via an intermediary, “a very good doctor friend, Ron, who is also close to Donald and Melania” and “was always one of the judges” at Miss Universe pageants when Trump ran them.

The friend spoke to Kellyanne Conway, a senior Trump adviser, who relayed the good news. Manafort was pardoned on 23 December 2020 – two weeks before the culmination of Trump’s attempt to overturn the election, the deadly US Capitol attack, an event Manafort does not address.

“It was like a switch was pressed,” Manafort writes, of telling his wife, Kathy, that he had been pardoned.

“We hugged and cried. I was free.”