The Bantams are still not out of danger at the wrong end of the table after goals from Kevin Nicholson, Gavin Tomlin and Billy Kee handed the win to the Gulls.
"We were so good in beating Macclesfield away on Tuesday and so poor in this game. We were beaten by a better side," Jackson said.
"This is the first time since I became manager that we have been outplayed for most of the game. We gave away two soft goals and I'm disappointed in terms of how we got beaten.
"This side is very up and down. I was confident going into the game, especially with the way we played at Macclesfield.
"It's important as a manager that you pick up points in front of your own fans. We have under-achieved this season. We haven't been good enough and that showed in this game."
Source: PA
Source: PA