The millionaire owner of Eddie Catz was exposed after police seized hundreds of clips taken in staff changing rooms and toilets.
Darren Johnson, 51, set up a network of peepholes with crimes dating back over the last 12 years.
Police discovered images of women undressing after they uncovered 12 years of secret filming at his Earlsfield site in South West London.
Around 700 clips were seized by police, taken in female staff changing rooms and toilets.
He was caught when two girls, aged 14, spotted him filming them on his phone at Putney Leisure Centre, West London, in June last year.
Johnson admitted voyeurism for sexual gratification at Kingston crown court. He was bailed for sentence.
Judge Timothy Lamb QC said: “The likely penalties include an immediate custodial sentence.”
Prosecutor Lauren Sales told the court:
“Two 14-year-old girls had attended a school swimming class and reported seeing an iPhone 6 pointing at them under their cubicle while they were in a state of undress. He was observed on CCTV walking around the leisure centre with no particular purpose.”
“He is the director of Eddie Catz, a soft play centre for children, and more images were found that he had taken in public lavatories open to both adults and children at the centre via peepholes.”
“There are also images from the adult female changing room at the centre.”
Eddie Catz was founded ten years ago, and has since opened branches in London, Leeds, Manchester and Bristol.
Johnson resigned as the director of the company last September after the allegations came to light, he no longer holds shares in the company.
Simon Ray, defending, said Johnson was receiving counselling from a psychosexual therapist.
Johnson will be sentenced on August 28, until his sentencing he is banned from all Eddie Catz centres as well as mixed us and women’s changing rooms. He has also been prevented from contacting victims, staff or witnesses and from using a camera, phone or video recorder to take images.