A mum’s ‘Santa Claus letter’ to stop her four-year-old swearing hilariously backfired.

When Gemma Doyle’s son Tommy started dropping the ‘F word’ regularly in Perth, Australia, she decided she needed a bit of bribery to try and stop this new habit.

Hilarious footage – filmed to send to Tommy’s grandma back in Ireland – shows Gemma reading a letter supposedly from Father Christmas explain to her child that good boys don’t swear.

Halfway through the recording, Gemma’s phone fell from the car windscreen causing Tommy to say ‘oh s**t’.

After finishing the letter, Tommy then cheekily asked Gemma if Santa can hear him if he says the F bomb ‘quietly’.

Gemma, who is originally from Ireland, said: “I knew I needed a bit of bribery but also I didn't want to scare him so I thought Santa was perfect.

“I hoped that he would stop swearing but now he just whispers the F word as he thinks Santa can't hear him

“I'm honestly not surprised. Sometimes he even just mouths the ‘F word’ but does not say it.”