Heat the oil in a large frying pan, add the onion and garlic and cook over a low heat for 3 minutes until slightly softened. Add the tomatoes, wine and sugar and season. Bring to the boil, then reduce the heat and simmer gently for 15–20 minutes, stirring occasionally and adding a little water if the sauce is too thick.
Meanwhile, cook the tagliatelle in a large saucepan of lightly salted boiling water for about 8 minutes, or until just tender.
Stir the seafood into the sauce and heat through for 2 minutes until piping hot. Drain the tagliatelle, then add to the seafood sauce and toss to coat. Serve sprinkled with the parsley.