qantas lounge 's ` smart casual ' dress code is now being enforced by staff .
since april 1 staff can refuse entry to customers dressed incorrectly .
customers have complained on social media after being turned away .
many of them said they were refused entry because of their thongs .
` the dress guidelines for our lounges are the same as most restaurants and club , ' qantas say .
but they refuse to define exactly what items are not allowed .