A hairdresser has been slammed online for giving his newborn son a flash haircut.

William Oliveira, a barber of 15 years, posted a video of himself giving his 18-day-old son a trim on social media, and it swiftly went viral, ratcheting up 26,700 views at the time of writing.

The new dad, who hails from the city of Sorocaba in the Brazilian state of Sao Paulo, posted the video on his Instagram page.

He captioned the clip: “18 days old and he’s already under the razor. Note: I didn’t touch the soft spot, he didn’t chafe, and he wasn’t injured. I did everything very carefully; I have 15 years of experience.”

However, some netizens were not impressed at the baby boy’s footballer haircut and criticised the dad, with one describing the short back and sides as “over the top”.

Others questioned why the dad felt the need to give his son a trim at all, with netizen ‘patricia_harket’ commenting: “I don’t see the point of cutting a baby’s hair.”

And others, such as ‘rosiimeryapp18gmail.com3’, questioned the man’s parenting, writing: “Clueless. Imagine what he’s going to do to his child in the future.”

While one netizen took a look at the trim and simply commented: “Never.”

However, the majority of comments were positive, praising the slick haircut and remarking on the newborn’s cuteness.

Flavia Nassif, a paediatrician at the Hospital Sirio-Libanes in the city of Sao Paulo and also a mother of two, told local media it is okay to cut babies’ hair.

She said: “The haircut can be given after a bath, when children tend to be more relaxed.”