The Hey Jude hitmakers called time on their career in 1970, seven years after their meteoric rise to global fame, and Yoko Ono is often held to blame for breaking up the foursome.
Fans have directed decades of anger towards Lennon's widow but MCCartney has now come to her defence, insisting Ono was a major influence on his former bandmate's songwriting.
In an interview to mark 50 years since the band released its first single Love Me Do, MCCartney tells Tv channel Al Jazeera English, "She certainly didn't break the group up, the group was breaking up... I don't think you can blame her for anything.
"When Yoko came along, part of her attraction was her avant-garde side, her view of things, so she showed (Lennon) another way to be, which was very attractive to him... So it was time for John to leave, he was definitely going to leave (one way or another)."