Radcliffe calls for tighter transgender rules to avoid 'manipulation'

British women's marathon world record holder Paul Radcliffe has warned of potential "manipulation" in top-level sport unless tighter rules are applied to transgender women.

International Olympic Committee guidelines state that athletes who transition from male to female should be allowed to compete without undergoing sex reassignment surgery but need to demonstrate their testosterone level has been below a certain level for at least a year.

The debate about whether it is fair for transgender women to compete in women's sport has come into sharp focus since a row developed between transgender cyclist Rachel McKinnon and former tennis player Martina Navratilova.

"Right now, transgender women are not a threat to female sport," Radcliffe told BBC Sport.

"But you would be naive if you thought that, by not putting in any rules, it couldn't come to that at some point in the future.

"People will manipulate this if there is an opening there to make money and win medals and we've seen the lengths people go to, the lengths Russia went to cheat in sport. "
"Both sides need to be protected, and calm, scientific research needs to be done. You can't have the two sides doing the research. It has to be neutral."