A man claimed he was "fat-shamed" by Qantas after being told he was too large for his pre-booked seat.

Darren Beales, from Geelong, claims the request to move seats on the flight from Melbourne to Brisbane amounted to public fat-shaming.

Mr Beales had pre-booked an exit row seat.

But when he boarded he asked cabin crew for a seat belt extension, as the regular belt is too small to fit him.

He was then told he couldn’t sit in the seat he had booked, and was made to move once everybody was on board.

"Pretty much she said that I cannot sit in this location, she said 'take a seat and someone will get back to me'," he told TODAY.

"So pretty much everyone was seated on the plane and she's came back up to me and she said, 'well, look, we've got another seat for you.'

A Qantas plane (stock image) (AAP)

"I paid for a window seat but I end up getting a lane (aisle) seat, pretty much I got hit every single time someone went down the laneway (aisle).

"She says, 'well, look, again airway regulations, you cannot sit in an exit seat, if you're disabled or, you know - or if you require an extended seatbelt.'

"It made me feel really belittled. I could have helped in the emergency."

Mr Beales said the rules were not made clear to him when he booked the special seat.

Qantas told nine.com.au in a statement guidelines on exit row safety are provided by the Civil Aviation Safety Authority.

Darren Beales, from Geelong, claims the request to move seats on the flight from Melbourne to Brisbane amounted to public fat-shaming. (AAP)

The CASA's website says passengers seated in exit rows must be "able bodied" and "appropriate" passengers who are able to help in an emergency.

Qantas' own guidelines online adds passengers sitting in the exit seats must not require the use of an infant or extension seat belt.