Inspired by the evergreen Stanley Gene, the Kumuls had the better of the opening period and looked set to cause a huge upset after tries from Rod Griffin, Jason Chan and George Kepa.
But with PNG tiring after the interval, England finally found some composure and claimed the win with a hat-trick from Lee Smith and further tries for Martin Gleeson and Ade Gardner.
It was a less than impressive display from an England side expected to go all the way to the final in Brisbane.
Captain Jamie Peacock admitted England had under-estimated Papua New Guinea. He told Sky Sports 2: "We knew we had to come out (after half-time) and play better and we did that.
"Papua New Guinea were very enthusiastic, I think we maybe didn't have enough respect.
"We were a bit wasteful with the ball.
"But we got the two points and need to move on to Australia next week.
"We've got a lot to work on but I think we did all right in the main."
Second-rower Gareth Ellis echoed Peacock's sentiments and admitted England were taken by surprise by their opponents.
"It was pleasing to finish in the manner that we did," he said.
"But I was disappointed with the manner of the performance.
"It was important we got the win.
"We knew we could improve, we knew we just had to step up our game.
"They probably shocked us a bit the way they played, all credit to them, they stuck in there."