It can be hard to get rid of stains on non-stick saucepans, but this solution usually shifts them.
To clean 1 saucepan
1 pint/570ml water
4 floz/115ml liquid bleach
2 tablespoons baking soda (bicarbonate of soda)
Few drops cooking oil
Pour the water and bleach into the stained saucepan and add the baking soda (bicarbonate of soda). Bring the solution to the boil over a high heat and continue to boil for 5 minutes. Then pour out the bleach solution, wash, rinse and dry the saucepan as usual and finally rub the surface with a little cooking oil on a paper towel.