throw under the bus
One is thrown under the bus when they are made the scapegoat or blamed for something that wasn't their responsibility in the first place. A coverup for your mistake.
Example:
Ruby Red, I didn't have time to do the business report, so I threw you under the bus and told the boss it was your job instead.
Ruby Red, I didn't have time to do the business report, so I threw you under the bus and told the boss it was your job instead.