Put the beans in a large bowl, cover with cold water and soak overnight. Rinse, then transfer to a saucepan, cover with cold water and cook for 45 minutes, or until just tender. Drain.
Meanwhile, heat the oil in a large saucepan. Add the leek and onion and cook over medium heat for 2–3 minutes until softened but not browned. Add the carrot, celery and zucchini and cook for 3–4 minutes. Add the tomato paste and stir for a further 1 minute, then pour in the stock and 1.25litres (5cups) water and bring to the boil. Reduce the heat to low and leave to simmer for 20 minutes.
Add the pumpkin, potato, parsley and kidney beans and simmer for a further 20 minutes, or until the vegetables are tender and the beans are cooked. Season to taste and serve with crusty bread.