I volunteer in a charity shop not far from where I live. It's a fairly affluent area and we get very good quality donations. Last week I sorted a whole bag of brand new, still with the tag on Joules/Boden/SeaSalt type things.
It's a busy wee shop and there is a constant stream of people dropping stuff off, and buying too. One lady was buying a fabulous hat to wear to a relative's wedding, she showed me the outfit it was to go with and we agreed it was perfect, and that she'd look amazing. I rang it through the till and said "And don't forget to tell them you got it here if anyone asks!"
She gave me the most evil stare I've had in a long time and said "As if I'd admit shopping in a charity shop!"
Why is it something to be ashamed of?? All of my friends love a good charity shop, we could all afford to buy new but there's nothing like knowing you've got a bargain. Our shop regularly has vintage clothing in which you just couldn't get in the shops anyway.