Goals from Joe Anyinsah, Danny Livesey and Ian Harte handed the Cumbrians a comfortable win at Brunton Park and Barnes was furious with his lacklustre troops.
"There are no excuses for players to perform the way they did, and the way we defended in the second half, where we were second to everything," he fumed. "I may have to put 15 and 16-year-olds in to show a bit of spirit and desire.
"We can't change anything because we haven't got any money to change anything. The players here have got to show more. There's no reason for them to play the way they did.
"I have belief in these players, but I am wondering if their belief is wavering. They have to want it more individually."