Fagan said Scottish Labour had to “change more than the faces at the top”.
The South Scotland MSP said the party had to be bold and get “squarely on the side of the working people of this country”.
“I am standing to unite our party, to back our movement, to seize this moment and rebuild Scottish Labour as a party for working people of Scotland,” he said.
Fagan said Scottish Labour needed to rediscover its “courage, boldness and imagination”.
“Let Scottish Labour decay, and when Labour decays, Scotland decays,” he said.
He called “caution and division” the party’s “deadly enemies”, saying “boldness, courage and unity are our only path”.
He also said Labour needed to “learn to win again”, arguing that it succeeded when it was “rooted in communities and serious about people’s lives”.
The new leader is due to be announced on 19 September.
