Tesco Tshirts dye running!

This is the letter I handed in to Tesco's today.

I purchased at least twenty tshirts from your online clothing site and your in-store clothes section in Kidderminster over the past year.
I noticed that half a dozen of the first purchases had a strange stain on the lower front of the shirts, I presumed at the time that I must have spilt something on them or mixed them with something bad in the washing machine, ( they have been washed at temperature stated in the label)
It wasn’t until a purchase back in April 2014 when I had a tshirt delivered and wore it the next day to a get together with friends, one of them mentioned that there was spots all over the bottom of my top, I looked down and noticed that my top was covered in marks, this top has never been in a washing machine and I had only owned it for one day, none of my other Tshirts or my families clothes have suffered with what looks like dye running on the Tshirts, it’s just the F&F brand Tshirts that was purchased from your store in person or online.
I have spoken to your customer service person who has recommended that I return these items to your store for you to inspect.
I like the clothing brand at Tesco but as you can imagine I am reluctant to purchase any new clothes from your store until this matter is resolved as your tops are lasting in some cases, no more than a few days before they start to fall apart.
Added to this, I purchased a Tshirt for my son (2 years old) one week ago and (F&F) and his shirt has followed suit.
I threw the first dozen shirts in the bin thinking I had ruined them, I have included 9 Tshirts with this letter for your to inspect.
I look forward to your response and solution.