A bride was left fuming after discovering her sister-in-law had eaten her wedding meal while she dashed off to the toilet.

The newlywed took to Mumsnet where she told fellow parents that she took only a few bites of her stuffed lamb dinner before going to the restroom.

The bride, whose name isn’t known, then returned to find her sister-in-law sitting in her seat finishing off her dinner.

“Walked in, saw my [sister-in-law] in my seat next to my new husband. Thought it was a bit cheeky but fair enough, I'd left him for a bit eating his meal,” the woman wrote.

"Approached the table, to find my SIL [sister-in-law] had FINISHED OFF MY PLATE!

“I didn't know what to do except stand there a bit shell-shocked! She apologised for being in my seat (didn't mention the food) and started to walk off. Well, my jaw must have been on the floor.

"I stopped her and asked her if she'd eaten my food and in her words, 'Yes, I figured you'd had enough as you're dieting and you walked off and left it.’

“I was speechless. She stood there with a smug look on her face and my husband sat there looking sheepish. I explained to her I'd simply gone to the toilet and she said, 'Oh sorry. Well, there's still dessert, I guess' and walked off!”

The furious bride then asked her new husband why he hadn’t intervened, Metro reports.

 “Asked my husband why the hell he let her sit there and eat my food and he turns bright red and said he thought I'd finished too. Great. Fuming.

"Didn't want to kick off on my wedding day and make a scene so sat back down in front of my empty plate, looking longingly around the room at the people eating slowly, who hadn't yet finished, and pretended everything was okay,” she said.

Horrified Mumsnet readers came to her defence, questioning why the sister-in-law had the nerve to eat the bride’s meal on her big day, Honey reports.

"I can’t believe she wasn’t embarrassed at all. That’s so awful," one user commented on the now-deleted post.

“I’d be furious!! Who does that?” another user said.

Sources: Metro, Fox, Honey