"The coalition is fighting the symptom of the problem, which is ISIS (the Islamic State organisation), without addressing the main cause, which is the regime," Syrian National Coalition President Hadi al-Bahra told The Guardian newspaper.
"People see coalition planes hitting ISIS targets but turning a blind eye to Assad's air force, which is using barrel bombs and rockets against civilian targets in Aleppo and elsewhere."
Bahra was speaking during a visit to London on Monday, during which he met with representatives of the 11 countries which support his coalition in its fight against Assad's regime.
Signup to our newsletter and follow us on Facebook and Twitter!
"People feel there is a hidden agenda and cooperation between the coalition and Assad's forces because Assad assumes he has a free hand," he told the newspaper.
Bahra also accused the coalition of "completely" ignoring fighters of the rebel Free Syrian Army.
"The whole operation has been confused. Air strikes will not be able to win the battle against extremism. You have to defeat ISIS on the ground," he said.
"And you have to deal with the main cause and source of extremism, which is the regime itself."