"We've got a lot to think through if we want to keep girls involved: the kit they wear, what showers they use," she said. "Even simple things like is there a decent smelling soap in the toilets? Boys don't give a toss about any of that, but girls do.
"Quite often in primary school you change in the classroom. If you're a self conscious girl and all the boys are in the classroom, there are some issues there."
Last August, the Government set out its Childhood Obesity Plan, which found that there has been a steady decrease in the percentage of girls aged eight to ten who exercise the recommended 60 minutes per day, from 22 per cent in 2008 to 16 per cent in 2012.
Public Health England commissioned the Youth Sport Trust and Loughborough University to research ways to increase physical activity in girls aged eight to ten.
The Youth Sport Trust, a charity which Baroness Campbell helped to set up and now chairs, ran a pilot project from March to September last year.
They found that there is a "steeper average decline" in physical activity of girls than their male peers at primary school. This September the Youth Sport Trust will roll out their new strategy for promoting PE at primary schools across the country, which focuses giving girls more choice about what kind of sports they do.
They also recommend that girls are taught sports separately to boys, with the emphasis on "fun and enjoyment" rather than competition.
Baroness Campbell said that sports lessons must not be confined to netball and hockey - which only appeal to a "small proportion" of girls - but should include more "feminine" options like dance, Zumba and trampolining.
"We've got a huge job to do to. We've got to learn to ask girls what they want," she said. "We've got to continue to provide those [traditional sports] but they are competitive and not all girls want to be competitive".
She said primary schools should offer a wider curriculum of sport, adding: "Dance would be a classic example, trampolining , Zumba, it's often things that in their mind relate to being feminine".
Baroness Campbell said that another major challenge with young girls is emotional illness.
"There is more self-harming than we have ever had before. If you ask any headteachers, this will tell you that this starts in primary school, mong nine and ten-year-olds," she said.
"We've got obesity and we've got this growing emotional stuff and my view is that physical activity is a counter balance for both physical fitness and emotional wellness".