That is quite a problem.
You have to keep his attention on you and make sure you are not putting too much pressure on him with the whip, try and use it less.
Do frequent transitions like 3-4 in one circle and changes of direction.
I completely disagree with Anne. NEVER lunge a horse with a bit. You will not only most likely hurt him if he moves his head or does anything with his head but he might start running even more because of that pain.
If the horse runs away it's not because of the equipment but the communication.
Lunge the horse with someone on him/her so that if he tries to do anything you have someone on him to bring him/her back into control.
Never lunge in a simple halter.
My mare used to do this. Using walls to block helps, whether round pen or at least two sides of arena and even ground poles. A lunging cavesson helps, using center ring. You can also use a regular halter with a ring on either side with climbing rope attaching them through the side halter attachments and lead rope ring under the chin (change sides when switch directions; the rope pulls tight but releases right away when the horse responds.
Long reining(1linge line each side) so can be used like reins to control
Use half of your arena and have as many people as possible able to help block it off with lunge whips he will learn that he cannot go past the circle boundaries.