How can I paint a varnished door in white?

I have varnished door, and I would like to paint them in white with gloss paint but when I do the varnish mixes with the paint. I have tried to take the varnish of but it is very hard. Is there anything I can put on top of the varnish prior to paint so that the varnish does not mix with paint?How can I paint a varnished door in white?
after prep and sanding use a special sealer that sticks to the varnish before undercoat then top coat. one brand of sealer is ';bin';. Ask your local paint shop. otherwise the paint will scratch off easily.How can I paint a varnished door in white?
sand it down and paint it.
Sand the doors with an electric sander using fine grit sandpaper. This will remove the glossy finish of the varnish and help the paint ';stick'; to the doors.
use paint remover ( you can find it easily at home depot or ace hardware ) to remove all the paint totally, then rinse with damp clothes, wait to dry then apply the new paint. different thinner will damage the old paint that's way you need to remove the old paint and re-paint the door. g luck