Ex-England boss Stuart Lancaster made an "almighty blunder" selecting Sam Burgess for the 2015 World Cup, according to the RFU's former of director of professional rugby Rob Andrew.
Burgess became the scapegoat for England's World Cup failure last year after he was fast-tracked into the squad following a switch from rugby league.
Lancaster has since said he would not have selected Burgess if he had known he would return to rugby league within a few weeks of England's World Cup exit.
Bath agreed a deal to release Burgess from the final two years of his three-year contract in November 2015 and he rejoined South Sydney Rabbitohs after just a season in rugby union.
Failure to get out of the group, coupled with losses to Wales and Australia, cost Lancaster his job and Andrew has pinpointed the problems.
In a section from his book, The Game of My Life: Battling for England in the Professional Era, published in The Telegraph, Andrew wrote: "If there was a problem team-wise in the run-up to the 2015 World Cup, a selectorial Achilles' heel, it was to be found in midfield.
"Try as he might, Stuart Lancaster could not settle on an optimum configuration. Which is where Sam Burgess came in, and where things went horribly wrong.
"I would not even begin to pin the blame for our embarrassing World Cup misfire on a single player, but the kerfuffle around the introduction of Burgess was undeniably the tipping point.
"To this day, I simply do not understand the thinking behind the fast-tracking of a player from international rugby league to international rugby union when so many of the things that had made him wildly successful in the 13-man game were of questionable relevance in the 15-man version.
"It was an almighty risk to select him in a World Cup squad on such extremely limited and highly questionable evidence and it proved to be an almighty blunder.
"Why did Stuart do it? He alone knows the truth of the matter. But all head coaches are control freaks in their own ways, especially around the matches and tournaments they know will define them, and Stuart became pretty dictatorial in the way he ran the show in 2015."
Andrew, who resigned from the RFU in April last year, also questioned the overall selection policy and said the World Cup exit was a "slow-motion car crash" following a build-up which lacked clarity and focus.