FINA executive-general Cornel Marculescu said they had reluctantly agreed to International Olympic Committee (IOC) demands for a change in the schedule for Beijing and to allow morning finals there.
The controversial move was driven by NBC, the television company that owns the rights for the Olympics in the United States, who wanted to be able to show the finals at prime-time in the US.
That has rised hopes in Australia that their Olympic broadcaster Channel 9 could arrange a similar deal for London.
Swimming is hugely popular in Australia and, along with the US, they are ranked among the world's top two nations.
But Marculescu said it would not happen again and declared the morning finals in Beijing a one-off.
He said: "I can say with no reservation that there is no way we will let morning finals happen in London at the Olympics in 2012.
"Our preference has always been evening finals and we showed that again in Melbourne last year at the World Championships.
"We are a key stakeholder of the Olympics and I can absolutely say no to morning finals happening again in the future."
"In none of our discussions with the organising committee in London has there been any talk of morning finals, and, again, this won't happen.
"We agreed to support the IOC as a strict one-off for the Games in Beijing, but that's the end of morning finals."