"undermine fairness" is correct and usable in written English.
You can use it when you want to express the idea that someone or something is causing or has caused fairness to be threatened or weakened. For example: "The court's decision to allow the accused to go free without a proper trial undermined fairness in the legal system."
Under the guise of protecting children, Congress has badly undermined fairness and judicial independence.
Left leaning critics of NHS reforms have long worried that market forces may undermine equity, or fairness of access, in health care.
"Creating a special and unique channel would undermine the fairness of the system," she said.
What "Happy Girl" had displayed was "undemocratic elements that are against democracy", such as disrespecting rules, organised cheating and special interests that undermine overall fairness.
He argues that in recent years we have been slipping without much reflection into relying upon markets in ways that undermine the fairness of our society.
In the words of one observer, the controversy has been "inadvertently revealing" of the incestuous processes that undermine the fairness and efficiency of Hong Kong's public capital markets.
"When you have a judicial candidate committing to being for the death penalty and against abortion, it really does undermine the fairness and integrity of the system".
On the other, it has been accused of presiding over payments to prosecution witnesses which defence lawyers say fundamentally undermine the fairness of many special court trials.
Steelers linebacker James Harrison was fined $75,000 for being a repeat offender on hits to the head, hits that, while damaging to players, do not aim to undermine the fairness of competition.
The efforts to rig the rate were "unjust and malicious, and could undermine the fairness of the markets," the Securities and Exchange Surveillance Commission of Japan said in a statement when recommending the nonfinancial penalties against UBS.
