Video of MAFS AU groom David using cheating wife Hayley's toothbrush to clean toilet shocks experts

Married At First Sight Australia groom David has defended a "barbaric" act of revenge on his cheating wife Hayley in which he used her toothbrush to clean a dirty toilet bowl. 

At the dinner party on Wednesday night's episode, Hayley admitted to kissing fellow participant Michael on a night out behind their respective partner's backs. 

Michael denied "making out" with Hayley, but by then David had already undertaken his plan to make his wife pay for her alleged infidelity. 

After confessing to the kiss and taking the heat from Michael's wife Stacey and the wider group, Hayley produced a toothbrush from her jumpsuit and threw it at David. 

She then showed the table a video on her phone which was filmed by David and revealed him using her toothbrush to scrub the toilet bowl's interior. 

The footage left the participants horrified and the experts audibly gagging as they watched from another room. 

"That is disgusting," expert Mel said. "That could make her very sick." 

Michael, accused of cheating with Hayley, said despite "how much he despised her", no one deserved to have their toothbrush used as a "toilet scour". 

Far from apologising for his actions, David stuck to his guns, saying his own friends had "done worse" to him. 

"You know why? Because practical jokes, there's no limit," he added. 

"I have confidence in the fact I've been nothing but a gentleman throughout this experiment," he told producers in an interview after storming out. 

Hayley ended the evening in tears, admitting she "f**ked up, but was so truthful" and dubbing David's stunt "barbaric" and "embarrassing". 

While the other participants had been divided about where to lay the blame in the cheating scandal, the group was unanimous in their condemnation of David's actions. 

"You f**ked up yes, but what happened to you was f**ked up, and you didn't deserve that," fellow bride Connie told Hayley. 

Married At First Sight Australia airs on Sundays at 7pm and Monday - Wednesday at 7.30pm on Three, with the episodes also available on ThreeNow.