Woodward had supported the ESL plan but changed his mind once he saw the huge backlash it had created within the game.
He telephoned United co-owner Joel Glazer on Monday to tell him he no longer wanted to be part of the process - and was left with no choice but to resign as executive vice-chairman after going against his bosses, says the Daily Star.
Woodward decided to fall on his own sword after realising he had made "one of the biggest mistakes of his professional career" in leading United's bid to be part of the doomed breakaway league that has torn the game in two.
Since resigning, the ESL plan has collapsed in dramatic fashion, leaving Woodward wondering if he acted in haste in giving up his job.
Glazer, who was going to become vice-chairman of the ESL, tried to talk him out of resigning, but Woodward's mind was made up.
Woodward feels huge remorse at being involved in the ESL project and has now admitted to colleagues that it was a huge mistake.
The former accountant and investment banker believes the final straw came when all those club owners involved in the ESL scheme refused to face the music or go public to justify the reasoning behind how the new league would benefit the sport.
Woodward now fears the damage done is irreparable - and that relationships between the 'Big Six' and rest of the top flight will never be healed.