Boil the potatoes until they are fork tender. Then drain, cool and remove potatoes skins. Cut the peeled potatoes into 1/4 inch pieces.
In a separate bowl, mix vinegar, olive oil, sugar, mustard, black pepper, water and season with salt. After the sugar and salt have dissolved, add the onions, bacon and parsley. Mix well then pour over potatoes.
Mix all ingredients together, cover and chill before serving.