Simon Darby made the claim as he clashed with the BBC's Andrew Neil on the Sunday Politics show over the loss of support for the far-right party and Mr Griffin's appearance with Greek neo-Nazis Golden Dawn.
He accused the BBC of "trying to put him (Mr Griffin) in prison twice merely for exposing the Muslim grooming scandal" but Mr Neil then asked why the BNP leader would not give an interview on the issue.
Mr Griffin posted a tweet apparently revealing the jury's judgments in the trial of a child sex ring, almost causing the case to collapse.
Asked why Mr Griffin would not give an interview, Mr Darby said: "Mr Griffin was in Syria. Nick was in Syria preventing a war, literally. He flew out to Damascus and prevented a war. He was instrumental in putting that letter across to the UK Parliament before that vote when we decided we wouldn't quite rightly interfere in Syria."