Even if you've never heard of the rule that it's not good form to wear white to a wedding, everyone knows that you should never try to upstage the bride.

So it was no wonder that one bride-to-be was somewhat upset to discover her future mother-in-law had purchased a wedding dress to wear on the big day.

But when her partner's mother was shocked to hear it was a problem, the confused bride took to Mumsnet for advice.

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A bride-to-be couldn't help feeling put out when her future mother-in-law announced she's bought a wedding dress to wear on the big day and turned to Mumsnet for advice (picture posed by model)

Posting under the username natalie204 she explained her soon to be mother-in-law (MIL) had shown her a photo of the dress and jacket she'd bought for the upcoming nuptials.

'It's a beautiful floor length white evening dress and white jacket,' she said. 'But I was brought up to never wear just white/cream to a wedding as a guest.

'I mentioned that it's not good etiquette to wear all white to a wedding. She was shocked and had never heard this before, my comment has now made things frosty.

'I know my family will mention to her on the day how it's not appropriate to be wearing white.'

She asked if it could be a regional thing as her partner and her family are from a different part of the country.

DollyBarton agreed that it's not good etiquette for guests, but said nobody would mistake the mother of the groom for the bride.

'I would think your MIL is feeling a bit down about what she obviously thought was a lovely outfit and now probably feel awkward about wearing after your comments,' she said.

'If she is generally nice, I'd go back and say her outfit is beautiful and you hope she wasn't put off it by your clumsy comment.'

MajesticSeaFlapFlap was also quite relaxed about it.

'I think it's fine. Everyone in the church knows it's you getting married,' she said.

'And I would hope that my family had been brought up with better manners and wouldn't mention it to cause any silliness at my wedding.'

Bambambini also balked at the prospect of the woman being taken to task by the bride's relatives.

'But why would your family actually bring this up on your wedding day with her? You OK with that?' she asked.

Heatherplant, however, had no such qualms and said she was sure plenty of people would mention it to her on the day.

'There is no way in the world she's done it by accident (unless she is from a totally different culture).'

While natalie204 may not have received a lot of support initially, she elaborated to explain that the dress was in fact an actual wedding gown.

'The dress is from Monsoon's bridal range,' she explained. 'A beautiful dress. I think she will look beautiful in it.

'Obviously it's not that people will think she's the bride. I've just been brought up to not wear only white/ivory/cream to a wedding.

'I can tell my family not to say something but they're adults.'

Of course, the news that she was planning to wear an actual wedding dress put things in a different light.

HouseworkIsASin wrote: 'She will look like Mrs Havisham and you will look gorgeous. Have a lovely wedding day!'

ToffeeForEveryone agreed that 'wearing a white dress to someone else's wedding is wildly inappropriate.

'That it is your MIL doing this adds an extra layer of weird.It's not some sort of arcane "rule", it's just common sense and common courtesy. The bride wears the white dress.

She added: 'What does soon to be husband think of his mother turning up to his wedding in a bridal gown? MIL has issues.'

Heirhelp agreed that only the bride should wear white and declared she would look 'a bit crazy', while CaroleService advised the poster to 'spill something on her. Or choose a scarlet wedding dress to really p* her off'.

TitaniasT*** didn't mince her words and said it was 'utter b******' that her mother-in-law didn't know the etiquette rules.

'Of course she did, and her frostiness was due to her banking on you not daring to challenge her on it, and you not complying,' she said.

'If it's any consolation, people will think she looks ridiculous. I was at a wedding years ago where the mother of the bride wore a long white dress and a white hat with a veil and everyone had a similar "my god, what on earth was she thinking?" reaction.'

However some still thought the bride-to-be was making a fuss over nothing.

SuburbanRhonda wrote: 'But surely if you're going to be such a stickler for tradition only a virgin bride would wear white.'

Ifailed asked: 'Which is more important, getting married or what people wear to the ceremony?