Dr Emily Lovegrove, a former piano teacher, believes if a child feels bullied they often are. And she has criticised schools for not promoting more positive thinking among pupils alleging bullying.
Dr Lovegrove told TES Cymru: "The responsibility does lie with the victim.
Saying it doesn't does them a disservice - it takes the power away from them."
Her controversial theory, in her new book Help! I'm Being Bullied, a self-help manual for parents, teachers and children, is in conflict with current thinking.
However, she bases her theory on her own research with teenagers, particularly regarding bullying over appearance.
"While adults may tell children to ignore taunts or dismiss personal remarks as just teasing, this is very real for children," she said.
"Most schools do have things in place to help with bullying, but most kids who have been bullied don't have the self-confidence to access them.
She added: "If you feel bad about yourself then your body language changes, and if you give off aggressive or submissive body language, other people react to that.
"It stops you being able to build social skills to deal with it."
Dr Lovegrove's top tips for beating bullying and taking control include:
* learning that everyone is bullied from time to time and learning to cope positively is a life skill;
* treating yourself with respect, showing others this is what you expect from them;
* seeing the best in people and realising that even bullies have some good qualities.
Dr Lovegrove said she retrained as a psychologist after being dismissed as "just a mum" while helping in her local school.
Her studies as a researcher at the University of West of England led to her working with children with physical disfigurements, both in the UK, including Great Ormond Street Hospital, and the USA.
"These children have the same type of concerns that all children have about their appearance. What we found is that the way you see yourself is the way people treat you," she said.
Her survey of 1,000 teenagers revealed that appearance was uppermost in their minds and many believed they were being bullied because of what they looked like.
"It's not just the archetypal child with red hair and glasses that gets bullied," she said.
"Many incredibly beautiful celebrities have revealed they were bullied too."
Dr Lovegrove is an anti-bullying consultant for Pembrokeshire LEA and a regular commentator on children's TV programmes, such as the BBC's Newsround.