It is said all children should be treated equally, but a new survey reveals mothers are more critical of their daughters than their sons.
A poll of more than 2,500 mothers reveals that while half (50.6%) think it is wrong to treat boys and girls differently, nearly nine in 10 (89.2%) believe parents do so.
More than half (54.9%) said they found it easiest to bond with their sons, the poll, conducted by parenting website Netmums, found.
The findings show that mothers are twice as likely to be critical of their daughters than their sons (21% compared to 11.5%).
And over a fifth (21.5%) said they let their sons get away with more, compared to 17.8% who said the same about their daughters.
More than one in four (26.9%) said they loved their sons in a different way to their daughters.
Crissy Duff, psychotherapeutic counsellor and a Netmums parent supporter, warned that differences in parenting can have a long-lasting effect on girls.
"Women in particular seem to carry the feelings of parental disapproval and negative typing into their adulthood," she said.
"The experience of receiving more negative reinforcements for stepping out of line than their male counterparts can lead women to view themselves as more needing of censure.
"This could be why women are far more self-critical than men, who have a more happy-go-lucky attitude when it comes to making mistakes and moving past them."
The poll found mothers were more likely to attribute positive personality traits to their sons than their daughters.
Boys were more likely to be described as funny, cheeky, playful and loving, while girls were more likely to be described as stroppy, eager to please, serious and argumentative.
Netmums founder Siobhan Freegard said: "As a mum of two boys and a girl, I know first-hand that, try as we might, it can be very hard to treat all of your children the same.
"This is a great wake-up call to mums to help break these gender cycles and even out the differences in how the sexes behave and think about themselves. It's a powerful call to change the current gender dynamics, which is a huge ask, but an achievable one."
Almost half of those questioned (47.8%) said their son was a mummy's boy, while just over a third (35.2%) said their daughter was a daddy's girl.
The Netmums parent support team came up with a list of tips for parents to help them treat their children equally.
They include being gender aware and ensuring the same rules within reason apply to every child, and giving children different play options - such as allowing girls to play with trains and building blocks, and boys to play with toy kitchens.
* The survey questioned 2,672 mothers through the Netmums website in September.