I didnt ask to use the scales, just went ahead and weighed said wrapper. Bought another (randomly selected) packet yesterday - the net weight was 391grams and therefore within the 2.5% error threshhold. I was going to go to Trading Standards my previous two purcheses weighing a net 385g against an advertised 400g e. As the item is a promoted item it will be going off the shelves this week. Ive decided to wait until it comes round again, probably in the next 4 or 5 months and then take another look. I'm convinced the 400g is not the avarage and that all packets weigh less than this. Thanks for everyones advice and comments - its been a learning curve.

gyzmo, ive sent you a pm

Using my home digital scales Gross Weight: 494g Contents: 385g Packaging: 109g (just) Using the scales in my local Post Office the packet weighs 108g. (This would mean the salmon contents would register as weighing that little bit less). Well the discrepancy between advertised net weight and actual net weight on the basis of my home scale measurements is 3.8961% according to my calculations. And when I look at the other packets they look similarly underweight. gyzmo, if your 'top of the head' figure of 3% is right then there is a case for Trading Standards to take up. However, my instinct is to approach this in a less confrontational way. I thought perhaps I might approach Customer Services and see what they can offer to correct the situation. And then of course I will go to Trading Standards afterwards. Any advice on how to approach Customer Services?

Is this supermarket selling its salmon underweight? On the packet it says "400g e" whereas contents regularly weigh 385g. What does " e " mean beside the "400g". If it means 'estimate' then I guess they are off the hook. However I dont understand how they can get away with this (It's an error of about 4% ). Alternatively, if they are diddling us , what can I do about this? Help and advice please.