Bring a large saucepan with water and a dash of milk to the boil and add the sweetcorn cobs. Reduce temperature to low and poach corn for about 15 minutes.
Drain the sweetcorn and allow to come to room temperature. Shave off the kernels with a sharp knife and place them in a salad bowl followed by the cucumber, feta, green pepper, onion and parsley and mix.
In a small bowl whisk together the oil, lemon juice, seasoning and sugar and pour over the salad. Toss and let marinate for 20 minutes before serving.