'Sexist pig:' Barack Obama's foul-mouthed thoughts on Donald Trump revealed

Barack Obama spent the first few years of Donald Trump's presidency respecting tradition and keeping his thoughts to himself.

While he broke his silence on the 2020 campaign trail for Joe Biden and publicly criticised the former reality star, nothing he said publicly compares to what he was telling people in private, a new book has revealed. 

Obama thought Trump was a "madman", "racist, sexist pig", "corrupt motherf***er" and a "f**king lunatic", author and journalist Edward-Isaac Dovere's new book Battle for the Soul: Inside the Democrats' Campaigns to Defeat Trump reportedly reveals

Dovere, a political journalist at The Atlantic, says the reactions were made to "big donors looking to squeeze a reaction out of him in exchange for the big checks they were writing to his foundation".

Before running for President, Trump spent years promoting a racist conspiracy theory that Obama was Kenyan-born Muslim. His presidency was dogged by accusations of racism and perceived support for white supremacist groups. 

The book is out on May 25. Dovere said there was more to it than just revealing Obama's potty-mouthed thoughts on Trump. 

"There's some cursing from him, but there's also depth and reflection," he wrote on Twitter.

There's also cursing from Jill Biden, the US First Lady, who reportedly told supporters future Vice President Kamala Harris should "go f**k yourself" after Harris attacked her husband during a debate in 2019.

Trump is yet to respond to early reports of what the book contains. The most statement on his personal Twitter-like website being a 909-word rant on the usual topics - the Mueller report, the 2016 and 2020 elections and criminal investigations into his business dealings.