The Investis IQ Corporate Website Ranking survey was conducted in the first quarter of the year, measuring website quality and performance against nearly 200 criteria.
Shell came first despite announcing a 62 per cent drop in profit on Wednesday, hit by a sharp fall in oil prices.
Aviva, which came out top last quarter, was second, with Sainsbury's, Tesco, BT and Vodafone making the top ten.
The overall standard of sites was driven up by improvements in corporate governance disclosure and IR content, both up eight per cent in the past six months. Careers information was the poorest performing category, reflecting the slowdown in recruitment.
The report said there remained significant room for improvement. Only 30 per cent of the FTSE 100 provided a meaningful account of the market environment in which they operate and fewer than 25 per cent provided a description of their key business drivers.