Speaking to Newsweek, Harvey Weinstein confessed that the British star was initially overlooked because of her filming commitments on Revolutionary Road.
"Before Kate came onboard, [producers] Anthony Minghella, myself and Scott Rudin had a conversation," he claimed. "I said 'Scott, she’s got Revolutionary Road. I think we should have insurance'."
Weinstein revealed that the part was first offered to Nicole Kidman, who was forced to abandon the project after falling pregnant. French actress Marion Cotillard was later screen tested in Berlin, while Naomi Watts was also approached.
However, Weinstein admitted that director Stephen Daldry was adamant that Winslet was the only person who could play former Nazi guard Hanna Schmitz.
Winslet has been nominated in the best actress category at this year's Oscars, which will be broadcast live on ABC this Sunday.