It is caused by the direction that the putter head is being swung in and the direction that the putter face is aiming in as it strikes the ball.

If you place an alignment pole, or golf club, on the floor to represent the line that you want to hit your putt down, a pushed putt would see the putter head swinging towards the ball from the inside of this line/pole. The putter head would cross the target line/pole as it struck the ball and then continue to the outside of the line/pole. The putter would be swinging from the inside of the target line to the outside of it. As the putter head is swinging in this direction, with the putter face aiming in that direction, the ball will travel straight but right of the hole.

To cure this, initially check the alignment of your feet. If your feet are aligned to the right of the hole this may be the cause of you pushing your putts. To check your alignment, place an alignment pole, or a golf club, across your toes when you have set up and are ready to putt. Now step back and look at where the pole is aiming. If you are aligned correctly the pole should be parallel to the target line. If the pole is aiming towards the target line, then you are aligning your feet incorrectly and this is why the putter is swinging from the inside to the outside of the target line, rather than along it. Ensure that you are aligned parallel to the target line.

Now check your stroke. To do this place the putter head next to the golf ball and position a tee peg on the far side of the toe of the putter and another just inside the heel, creating a tee peg gate that the putter head just fits inside of. Remove the golf ball and place an alignment pole to represent the target line. Position two more tee pegs, one in line with the tee peg on the outside of the alignment pole and the other in line with the tee peg on the inside of the alignment pole, but three inches to the right.

Repeat this again, three inches to the right and then repeat again one final time, three inches right again. This will create a tee peg channel for you to swing the putter head through. Place the golf ball on the middle of the channel and then putt. Work on swinging the putter head directly through the middle of the tee peg channel, whilst keeping the putter face aiming down the middle of the channel, along the target line.

This will get you to hit your putts much straighter and you will improve your accuracy and see that you are no longer missing putts on the right.