Peel carrots and onion. Cut both into fine cubes. Peel garlic and chop finely. Cut bacon into fine cubes. Heat oil in a large pot. Fry the bacon and onion until golden brown.
Wash the lentils, drain and put them in the pot with the carrots, garlic and tomatoes. Bring to the boil. Pour in the broth. Season with salt and pepper. Add sausages and simmer for about 30 minutes at medium heat.
In the meantime, chop parsley finely except for a few leaves for garnishing and add to the lentil soup. Season to taste with salt, pepper and vinegar. Take the sausages out of the soup and cut them into slices.
Add to the soup again and serve.