'ever more stringent' is correct and usable in written English.
You can use 'ever more stringent' to describe something that is becoming increasingly strict or severe. For example: "Due to the increase in Covid-19 cases, health and safety regulations have become ever more stringent."
Back in the 2001, the IMF was pushing Argentina to pursue ever more stringent austerity measures.
The regulations that govern the claims advertisers can make are becoming ever more stringent.
Within the petroleum refining and petrochemical industries, catalysts provide the opportunity for drop-in solutions for addressing ever more stringent product quality and environmental specifications.
And so it went for 5,000 years, with the criteria for death becoming ever more stringent.
What happened in Paris shows that an ever more stringent security arsenal is not a guarantee of national safety.
Jobseeker's allowance is now a mere 15% of average earnings and subject to ever more stringent conditions, backed by sanctions.
Finally, leadership tends to take too much responsibility for success by planning ever more-complex strategies and ever more-stringent implementation plans, while the middle- and lower-level managers see these efforts, feel helpless, and back off from taking responsibility.
The consumer taste issue will only become more acute as ever-more stringent CO2 limits are needed to stave off the most disruptive impacts of climate change.
These range from securing and preserving access to sufficient quantities of high-quality water and limiting production disruptions, to meeting ever-more stringent wastewater discharge standards.
I fear that if the NSA tries to impose ever-more stringent controls, this will create even more disgruntled workers and a larger pool of anomalies.
The tobacco industry perfected this approach in the 1970s, demanding ever-more stringent levels of proof that smoking caused cancer in order to delay government regulation of their products.
