Ace Chinese badminton player Lin Dan has apologised for an extra-marital affair he had when his wife was pregnant, shortly after his "intimate" photos with a model went viral on social media.

Ren Hai, a professor from the Olympic Research Centre with Beijing Sport University, told the Global Times that the scandal has damaged Lin's image since the public expected him to not only be a good player but also a decent man in life.

"The personal life of celebrities has a direct influence on their commercial value. The sponsors have a right to pull back their sponsorship if they deem the effect to be damaging," Ren said.