Shane's angry post has since gone viral, racking up thousands of likes and shares on social media.
Shane said: "I went down to the store three days before my son’s birthday to order the cake. I explained to them we wanted a frog theme, as my son loves frogs.
"They told me it could done, no worries at all. He wrote down everything I said and said it would be ready by Sunday morning. I was very excited to see it.
“I went down to pick it up on the morning of Mason’s birthday party. I was in a rush getting extra supplies and didn’t actually check it at the store because it was in a huge box.
“I just assumed it would be fine. When I got home, I opened it up with my wife and we were both mortified.
“They had this tiny little number three, along with a smiley face, all written in green icing. It would have taken five seconds to do.
“Amy was very upset, as our guests were arriving in a couple of hours. We thought we would have to try and bake something else.
“I decided to just ring Woolworths to see if they could fix it. I explained the situation but was told that they didn’t ‘decorate’ cakes.
“They have other pre-made cakes for sale that all looked lovely, so I thought they would do a good job.
“They do this every day for a living. Surely, they could have done something better than this.”
Shane said the ‘pathetic’ cake forced his family to seek help from another cake decorator who thankfully ‘saved’ his son’s birthday cake just twenty minutes before his guests arrived.
And despite the initial ‘disaster’, Shane said his son Mason still had a great birthday party and enjoyed eating the ‘repaired’ version of the cake.
He said: “A cake is an integral part of any child’s birthday party. You want a nice one, so you’re able to remember it and take photos.
“I was most disappointed with just the lack of effort. It seemed like they didn’t even care.
“It was a disgrace. I will never be buying cakes from Woolworths again.”
A spokesperson for Woolworths said: "We're sorry to have disappointed the customer with our cake decorating, particularly on such a special day for the family.
"We've been in contact with the customer to apologise and provided them with a $50 AUD gift card."