Kirstie Allsopp has criticised the National Childbirth Trust, describing it as "a politicised, dogmatic and scary organisation".
The TV presenter attacked the charity over its pro-natural birth stance in tweets to her 272,000 followers on Twitter.
Miss Allsopp, 41, who has a home in Broadhembury, near Honiton, has two sons, Bay, six, and Oscar, four, with her property developer partner Ben Andersen. She made the comments after listening to a discussion on Radio 4's Today programme involving the chief executive of the NCT and an author on childbirth.
Miss Allsopp, whose two sons were both delivered by caesarean, suggested on Twitter that the NCT was failing to offer enough information about the procedure in their antenatal classes, which are attended by more than 100,000 couples every year.
She wrote: "Turn to BBC Radio 4 for talk of a book about all the absurd myths surrounding pregnancy & birth. More NCT b******* as usual though. Lots of people have good NCT experiences, but many don't. This is a very politicised, dogmatic and in my experience, scary organisation."
The NCT's chief executive, Belinda Phipps, said yesterday: "NCT antenatal courses cover all the topics that are relevant to expectant and new parents, including giving birth by caesarean section. The content of the course is also influenced by the expressed needs and wants of the small group attending, which means that some topics may be discussed at more length than others.
"We encourage feedback on all our courses and ask anyone who isn't satisfied to contact us directly."
Miss Allsopp told the Daily Mail: "I feel that most women want to have a natural birth – I wanted to do that – but I was told I couldn't for various reasons.
'Sometimes it isn't possible and a caesarean section is necessary. I feel that women should be prepared for that too and not made to feel that they have failed in some way if they don't give birth naturally."