Victoria and David Beckham's Polished Rep Under Threat by Tell-All Book

An explosive new book about Victoria and David Beckham promises to throw loads of shade on the polished Brand Beckham with alleged details of their marriage.

"The House of Beckham: Money, Sex, and Power," penned by British investigative biographer Tom Bower, is dropping this June -- and if you've been curious about David's bedroom antics, especially those rumored affairs ... the author says you're in for a treat.

Even though V & B sat down amicably for 2 lengthy chats with a senior member of his team, Bower didn't meet them personally ... claiming he knew they'd end up turning him down.

Plus, he claims to have gathered plenty of juicy revelations from a bunch of other sources to bring the tell-all book to life -- so he thinks he didn't actually need to speak to Victoria or David.

But, Tom's not making any bold claims about the book's impact on their ironclad image. He tells The Mirror, "It's an astonishing achievement to have maintained their image despite their ups and downs, but whether it's damaging, the public will decide. What do they really represent? And, that's what the book answers."

HarperCollins is set to publish the book ... promoting it as a deep dive into how these "business-savvy cultural icons" navigated their journey through the glitzy realms of "money, sex, and power."

All of DB's Rebecca Loos affair claims from 2 decades earlier will most likely be covered in-depth -- especially since it was glossed over in the couple's Netflix doc last year.