Cook the pasta in salted boiling water according to the packet instructions, about 10-12 minutes. Drain and rinse under cold water to cool.
In a large bowl, combine the mayonnaise, Dijon mustard and white wine vinegar. Stir until smooth.
Add the drained tuna, sweetcorn, red onion, red pepper and parsley to the bowl.
Add the cooled pasta and toss everything together until well coated in the dressing.
Season with salt and black pepper to taste. Serve immediately or chill for 30 minutes for the flavours to develop.