Fat Les were formed by Allen (below bottom), artist Damien Hirst (below left) and Blur guitarist Alex James (below right) for the World Cup 1998 track 'Vindaloo'.
Allen explained that the new song will be released for the Olympics in London as a statement against corporate sponsorship at the Games.
He said: "Apparently during the build-up to and during the Olympics we are not allowed to demonstrate nor are we allowed to have in our houses any politically inflammatory posters that could be used in a demonstration.
"Now I think people expressing themselves through sporting activity and healthy competition is wonderful but I don't believe sport should be used to prop up and endorse rampant capitalism and the idea that 70% of spectators will have to navigate their way through Westfield is sickening."
'The Official Fit Les Olympics Anthem' will be released without Alex James, but with former X Factor contestant Rowetta and Matt Eaton.
Fat Les also released novelty festive track 'Naughty Christmas (Goblin in the Office)' in 1998, along with a version of the hymn 'Jerusalem' for Euro 2000.
Watch the video for 'Vindaloo' below: