Isaac Armitage had been playing in a black and purple fairy outfit with his little sister when he answered the door to the un-named driver.
Mum Wendy Armitage, 36, said she overheard the driver say to Isaac: ‘Someone needs to take you to one side and have a word with you, you can’t be a fairy, you should be a superhero.’
Isaac, who wore the fun outfit a few times a week, has been left upset by the incident and Armitage said he now rarely wants to dress up.
“I just couldn’t believe it when I heard it,” Armitage, from Effingham, Surrey, said.
“If [the driver] had said it’s unusual to be a fairy, we wouldn’t have have thought too much of it,”Armitage continued.
“But saying someone should take Isaac to one side implies he was doing something wrong.
“I feel disappointed that there are still people in this world that ask questions like that and and think it is their right to tell other people what they can and cannot wear.
“My son has been more reluctant to wear his fairy dress since, he has only worn it once or twice whereas he used to wear it all the time.”
The delivery driver had gone to Armitage’s house on 13 August. She was upstairs in bed as she has a chronic pain condition that affects her mobility.
Her husband Laurence Armitage, 35, had been in the kitchen unpacking the shopping after Isaac answered the door to the driver.
“He was wearing a fairy dress up outfit and so was his little sister,” explained Armitage.
“He likes answering the door when he knows the delivery driver is coming.
“I was upstairs having a bed day as I have a disability and heard the driver say to my son: ‘Where’s mummy?’ and Isaac said I was upstairs.
“So he asked Isaac: ‘Are you the doctor and your sister the nurse?’, which I thought was a bit sexist, and he said: ‘Why are you wearing a fairy dress?’
“Isaac said: ‘Because I am being a fairy’ and the driver said someone should take him to one side and have a word with him.”
Isaac first developed a love of dressing up at the age of two after coming across a big box of outfits at a parent toddler group. As well as his fairy outfit, he also regularly dresses as Darth Vader, a doctor, nurse and vet.
The family have a bag of mixed dressing up clothes and Isaac likes the dresses and the fireman outfit.
“He’s definitely very imaginative,” Armitage said. “He’s always playing make believe and being different characters. Even if he doesn’t have the dress up things to do it.
“When he didn’t have a magic wand, he made one himself and he will often cut up bits of cardboard to make props.”
The mum said she has since tried to explain to both of her children why the man said what he did. But as they are so young they have been left confused by what happened.
She added: “I tried to contact Sainsbury’s customer service afterwards and couldn’t get through, so wrote on their Facebook page where they replied to me.
“I got a reply which said: ‘Sorry about that!’ and asked me to send them a message explaining what happened and they said they’ll look into it.
“We didn’t get any real apology though and I asked what is going to happen from here and they said it has been reported to the online manager at that store for them to look into it.”
Armitage now hopes the delivery driver gets “re-trained” so that no other child should be made to feel the same way.
A spokeswoman for Sainsbury’s said: “We have apologised to the customer for these inappropriate remarks and taken suitable action with the colleague.”