Tesco carrier bags.
I did a Tesco shop yesterday and thought I would walk back to the campus, as it only takes 20 minutes and I had two bags (a 9p bag for life and a carrier bag). Before I even got to the campus both handles went on my carrier bag, and so a 2nd year carried my heavier bag for me because I had to hold this other bag =P Then my bag for life ripped itself along the side (I had only just bought it!). Then my donuts fell out and got squashed. We got to the campus and then a hole appeared in my carrier bag and my milk fell out so the plastic cracked along the bottom, and that went everywhere. Then my cucumber fell out the same hole which I was trying to hold together. And then my yoghurts fell out of the bag for life and opened themselves because that bag had ripped again. Finally, a pasty fell out, then I made it back to my room (eventually, after leaving my shopping outside and making several trips). And some guy holding 6 Sainsbury's carrier bags walked past me with all bags still intact ¬¬
Rubbish biodegradable bags. Even the bag for life was a load of rubbish as it didn't even survive one trip! I won't be forgetting my canvas shopping bags again. It was so annoying, and since then I've seen lots of people cradling broken Tesco bags on their way back to campus.