The phrase "a consistent ally of" is correct and usable in written English.
You can use it to describe someone or something that reliably supports or stands by another person or group over time.
Example: "Throughout the years, she has been a consistent ally of the environmental movement, advocating for sustainable practices."
Alternatives: "a steadfast supporter of" or "a loyal partner of".
China – a consistent ally of Moscow – abstained.
The lone dissenter was Senator John B. Breaux, Democrat of Louisiana, who has been a consistent ally of the broadcasters.
Even the U.S. Chamber of Commerce, a consistent ally of the Republican majority, questioned the House's course.
After the latest letter, Senator Dianne Feinstein, another judiciary committee Democrat and a consistent ally of the security agencies, said she found Comey's intervention "even more troubling".
Speaking today on the NBC News program "Meet the Press," Senator Carl Levin, Democrat of Michigan, complained, "We have sort of hot and cold support from the Saudis when it comes to this war on terrorism," and added, "They've not been a consistent ally of ours".
Congressional aides, former regulators and lobbyists familiar with Mr. Kerry's record say that unlike other senators who play a guiding role in telecommunications policies affecting billions of dollars of commerce, Mr. Kerry has not been a consistent ally of any particular cause or industry.
"It sounds like this report restates the problems, offers very little solutions and dumps the issue into the lap of the Legislature and the governor," said Senator Nicholas A. Spano, a Westchester County Republican who is a consistent ally to the governor.
Obama needs a consistent ally to fight his corner should he redouble his efforts in mediating the Israeli-Palestinian conflict in 2010, and won't want to risk the instability of forcing reform.
Egypt has been a consistent ally and Burma's reforms, as well as fear of a rising China, have brought the country back into the U.S. fold.
The group has rejected media reporting on psychologists' complicity in torture; suppressed internal dissent from anti-torture doctors; cleared members of wrongdoing; and portrayed itself as a consistent ally against abuse.
Australia has, in other words, been a consistent ally.
