Former FIFA president Sepp Blatter has claimed that the use of the video assistant referee (VAR) system at this summer's World Cup is "not very clever".
Blatter's permanent successor, Gianni Infantino, confirmed in March that world football's governing body had approved the use of VAR in Russia.
However, Blatter says fans "don't feel comfortable" with the system.
"For a purist in football, as I am, I think it is an innovation which is going too fast," the 82-year-old told BBC Sport.
"Most of the referees have never worked this system. To go to the World Cup and introduce this system in the World Cup, I think it is not very clever.
"I don't feel comfortable, definitely not, and spectators don't feel comfortable."