A furious row over the right of men who identify as women to use female-only train compartments has pitted Sir Winston Churchill’s grandson against the might of Mumsnet.

The dispute erupted after the operator of the Caledonian Sleeper, which runs overnight between London and Scotland, said that passengers who were born male but ‘self-identify’ as female could sleep in cabins reserved for women.

The move caused uproar on the Mumsnet internet forum, where users complained that their safety could be endangered.

Mumsnet argued that the safety of women could be compromised if passengers who were born male but ‘self-identify’ as female sleep in cabins reserved for females

Mumsnet argues that they do not share the same faith as Mr Soames when it comes to 'male train passengers' behaving themselves in women-only berths

Mr Soames argued on Twitter that people would not say that they are a woman when in fact they are a man - because Caledonian train passengers are not that deceitful

An attempt to defuse the row by Rupert Soames, the chief executive of Serco – which took over the running of the sleeper service three years ago – led to claims that he had been ‘patronising’.

Mr Soames, whose grandfather was the great wartime Prime Minister, was reduced to pleading that the cabins had emergency buttons.

It is the latest controversy over transgender rights and follows the decision by a female-only swimming pond on Hampstead Heath, North London, to welcome men ‘transitioning’ to women.

Proposals to make it easier for people to change gender also prompted two feminists to protest by attending a men-only swimming session at a leisure centre in South London.

The Caledonian is one of only two railway sleeper services left in the UK - it shuttles between London and stations in Scotland including Edinburgh, Glasgow and Aberdeen

Serco took over the franchise of the Caledonian service from ScotRail - a £150 million revamp is due in October which will introduce en suite cabins and double beds

Mr Soames argued that if a single woman was uncomfortable with the other person with whom they shared a cabin, they would be entitled to move

The sleeper service row began after a Mumsnet user posted Serco’s response to an enquiry about whether women could be forced to share cabins with men who define themselves as female.

It said: ‘Guests travel with the Caledonian Sleeper in shared accommodation for men-only or women-only; the service is provided on the basis of the gender that the individual self-identifies with.’

The Mumsnet user wrote: ‘I don’t think I’d feel comfortable with this at all and it’s yet another example of women’s spaces being erased.’

Mr Soames responded on Twitter, writing: ‘I think you are referring to the possibility that people may say that they are a woman when in fact they are a man – sigh.’

He said his passengers would not do that, because they were not ‘deceitful’.

A user called Helen Wheels then asked: ‘You know them all personally? Otherwise, that’s a statement for which you have zero evidence. You might as well say, “No rapist has ever travelled on a train.” ’

A group called the Caithness Purported Feminists told Mr Soames: ‘We do not share the same faith you do in male train passengers.’

And another Twitter user wrote: ‘Many predatory men have identified as women to gain access to female spaces. I suggest you educate yourself properly before dismissing valid concerns with a patronising “sigh”.’

Mr Soames tweeted that his staff were ‘v attentive and watchful; all cabins have call buttons; if a single woman was uncomfortable with the other person they would be moved to another cabin’.

The Caledonian, one of only two railway sleeper services left in the UK, shuttles between the capital and stations in Scotland including Edinburgh, Glasgow and Aberdeen.

Serco took over the franchise from ScotRail. A £150 million revamp in October will introduce en suite cabins and double beds.

A Serco spokesman said: 'Everyone is greeted personally and shown to their cabin on the Caledonian Sleeper by our excellent and highly attentive staff.

‘Anyone travelling can choose to book a cabin alone and the option to share with another person of the same sex is being phased out in autumn with the arrival of the new carriages.'

Mr Soames, whose eldest brother Nicholas is a Tory MP, is the son of the late Sir Christopher Soames, an ambassador to France; his mother, Mary, the youngest of Sir Winston’s five children, died in 2014