Heat olive oil in a large, heavy-bottomed saucepan over medium-low heat. Cook the leek and garlic until soft; about 5 minutes. Stir in the rice and cook for 5 minutes more; stirring frequently.
Pour in 1 1/2 cups of the chicken stock and bring to a boil over high heat; stirring occasionally. Reduce heat to medium-low and simmer uncovered for 5 minutes; continuing to stir. Pour in the remaining chicken stock and wine; increase heat to medium and cook for about 5 more minutes stirring constantly.
Add the scallops, prawns, peas and red capsicum. Cook, stirring constantly until the remaining liquid is almost absorbed and the seafood has cooked; about 5 minutes. When the rice is just tender and slightly creamy season with Parmesan cheese, basil, lemon juice and pepper.