A dad taken to Facebook to vent his frustration after Woolworths allegedly ruined his son's specially made frog-themed birthday cake with its "pathetic" decorating.

Shane Hallford, 43, forked out a hefty $50 on the cake to help celebrate Mason's third birthday in Tamworth, NSW.

The dad-of-two said his request for in-store bakers to supply a frog-themed birthday cake was confirmed by the supermarket three days prior to picking it up.

But the police officer and his wife Amy, 29, were horrified to discover that their son's cake looked "nothing" like the treat they had specified.

Instead of the colourful number three and big green frog they had both envisioned, the "mortified" parents were met with a "pathetic" smiley face and small number three clumsily piped in green icing.

The $50 cake created by Woolworths.

Luckily, a sympathetic cake decorator mate came to their rescue, and managed to repair the botched cake just in time for Mason's party.

"I went down to the store three days before my son's birthday to order the cake," he said.

"I explained to them we wanted a frog theme, as my son loves frogs. They told me it could be 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."

But as he was in a rush on the morning of Mason's birthday party, he didn't actually check it at the store.

A friend came to the rescue and fixed Mason's cake before his birthday party.

"I just assumed it would be fine. When I got home, I opened it up with my wife and we were both mortified," he said.

"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."

Shane called Woolworths to complain, and see if it could be fixed.

But he says he was told the supermarket chain does not "decorate" cakes.

He said that after seeing other pre-made cakes in the Tamworth store "that all looked lovely, 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."

Despite the initial "disaster", Mr Hallford said Mason still had a great birthday party and enjoyed eating the hastily repaired version of the cake.

He added: "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."

The post to the Woolworths Facebook page has received more than 6200 comments and 5000 likes.

Woolworths says they have since reached out the family and provided a virtual refund to them.

"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 Gift Card," they said in a statement.