"There's been a lot of research that says that images that young people have about what careers they want to do are formed when they are about four or five.
"If you are promoting that image we might be stopping people wanting to apply for the fire service 20 years down the line."
Sam will be replaced by in-house creations, the fire extinguisher-shaped Freddy, Filbert and Penelope.
The decision has been backed by the London Fire Brigade and the Fire Brigades Union (FBU).
"We're not bothered about Fireman Sam, we're bothered by the subconscious message the term 'fireman' has created as an issue in our recruitment," Ben Selby, the FBU's executive council member said.
"Fireman is an archaic term that doesn't reflect the reality of the job — I think it's time the producers of the show accept that."
Set in the fictional Welsh town Pontypandy, Fireman Sam has been a fixture of children's TV since its creation in the 1980s by London firefighter Dave Jones.
Mr Jones told the BBC we now live in a "very PC world".
"I joined the fire brigade on my 18th birthday (and) if I had said I was a firefighter I would have been slapped down by my colleagues saying 'you are not a superhero, you are just a fireman'."
Piers Morgan blasted Lincolnshire fire chief Britzman on Good Morning Britain.
The vocal TV personality asked Britzman if he would give up his position to a woman if he felt so strongly about inclusivity.
Fans have called the choice ridiculous, comparing the new mascots to coloured frogs and giant male contraceptives and blaming the "woke brigade" and feminists.
This isn't the first time the show has faced claims of sexism, despite now including disabled and ethnic minority characters, alongside female firefighter Penny Morris.
A 2017 campaign to rename the show Firefighter Sam was backed by London mayor Sadiq Khan, though the change never came to fruition.
