Alex Bertie, 21, describes himself as "just another LGBT guy from the UK making videos in his bedroom" Picture: YouTube.com

London - Young YouTube stars who enthuse about changing sex are making being transgender "cool", parents fear.

Briton Alex Bertie, 21, describes himself as "just another LGBT guy from the UK making videos in his bedroom". He began posting about transitioning from female to male almost a decade ago.

In one video, Bertie, who has more than 300 000 followers, talks about how taking testosterone "has been pretty amazing".

One mother, who spoke anonymously, said her 13-year-old daughter watched his videos "obsessively" before saying she wanted to become a boy.

Another transgender YouTube star, American Miles McKenna, 21, has one million subscribers to his online channel called Miles Chronicles.

During the course of his many broadcasts, he advises his young fans that "in the future gender is going to be an outdated concept".

Stephanie Arai-Davies, from Transgender Trend, said: "Young girls are being heavily influenced by social media. When they get older they’ll regret it if they take any hormones that they won’t be able to reverse."