"One little accident and it could be the end of your Tour," Froome said. "In my opinion it was a bit dangerous from Alberto to ride like that, it's not good."
On the final descent down from the Col de Manse, Froome and Contador were undone by a sharp right turn as the Brit chased after the Spaniard.
Froome went off the left side of the road and had to plant his left foot on the ground to stop from toppling off completely. Contador also lost balance and hit his knee on the ground before quickly jumping back up on the bike.
"It actually put me in danger because I had to go off the road to avoid him," Froome said. "He couldn't control his own speed and crashed."
Contador, the 2007 and '09 champion stripped of his '10 title for doping, defended himself.
"It was really difficult. In normal conditions I wouldn't have slipped like that, but it was very difficult terrain and the bike got away from me," he said. "Sometimes you have to go for it, whether it's at the start or the end of a stage."
Froome seemed to be more than a little exasperated, and his radar will be on red alert in the days to come.
"All teams are starting to get desperate now and they're taking uncalculated risks," he said. "In my mind this Tour is not over until I cross the final line on the Champs-Elysees."
Tour de France
P Stage 17
Wednesday, 6 a.m.
TV • NBCSN
1. Chris Froome
2. Bauke Mollema -4:14
3. Alberto Contador -4:25
4. Roman Kreuziger -4:28
5. Nairo Quintana -5:47