Tanya Willis was banned from a fairground ride called Colossus because her 36L breasts would not fit under the safety bar.
The humiliated mum-of-one then had to walk past hundreds of people queuing for the ride at Thorpe Park in Surrey.
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Tanya, 22, said: "They should realise that not everyone has a B cup. Some of us are bigger than that.
"I'm not fat but the safety bars and seats are not designed for large-breasted women.
"It was really embarrassing having to be chucked off a ride and do a walk of shame past everyone. It ruined my day and I wasn't even offered a refund."
Size 18 Tanya paid £28.99 for her ticket but had to sit watching her family enjoy themselves on the ride.
She said: "We had travelled all the way there so there was no point in them missing out because the ride could not accommodate my breasts."
The former doctor's surgery worker from London then tried to go on another ride called Rush – but again staff said her breasts were too big.
"It will not start unless all restraints are locked. We have restriction boards at each attraction."