He claimed Shaw's reported wages of around Â£100,000 a week were way too large for a player who only made his Premier League debut in November 2012.
"If we pay to a 19-year-old boy what we were being asked for, to sign Luke Shaw, we are dead," Mourinho was quotes as saying in several national newspapers.
"We would have killed our stability with financial fair play and killed the stability in our dressing room, because when you pay that much to a 19-year-old kid - a good player, fantastic player - but when you pay that amount of money, the next day, we would have had players knocking on our door.
"They would have been saying, 'How is it possible I play 200 games for this club, won this and that, yet a 19-year-old comes here and gets more money than I get?"'
For the big stories and the banter follow us on Twitter: @tribalfootball