I am in the process of of finding out. At the moment it runs -
1st Place Sainsbury - 2nd Place ASDA - 3rd Place Tesco - 4th Place Morissons
Sainsbury have the most MSC (Fish Sustainability) Labels on products by a long way, ASDA is second, soon I hope to have all the number and add them up and then ta tad you will know.
Its just a guess but I think Tesco's may be in the lead with Carbon labels, if you know different then drop me a line.