The brothers Noel and Liam Gallagher and their colleagues have earned �40m since Oasis released their first single, Supersonic, in 1994. Members of the band will eventually receive nearly half the money.

The only other British quintet to come close are the Spice Girls, who have made �9m in less than a year. They will profit less than Oasis as they do not write all their own songs.

Cliff Dane, an accountant and author of the study, said Oasis were one of the most financially mysterious groups he had tracked.

"You can easily follow the paper trail of vintage acts such as Pink Floyd or Queen. But the Oasis company accounts, which have just been released, conceal a lot more than they reveal."

The band earn only 40% of their money in Britain and that percentage will shrink further this autumn when Oasis tour America for a ninth time. Unlike the Spice Girls, who have replaced Britpop rivals Blur as the Gallaghers' main target for verbal abuse, the brothers have never entirely won over the Americans.

"Half their money comes from record sales, largely from the two albums Definitely Maybe and What's the Story (Morning Glory), but they have made �6m from live shows.

"These boys may play the fool in public, but behind the scenes they know they are a money machine," said Dane, author of Rock Accounts.

Noel Gallagher is the only band member to have his own company to separate his song-writing royalties, due every time Oasis records are played on radio.

Last week, in a rare interview, Marcus Russell, the Oasis manager, told The Sunday Times about the "secret strategy" behind Oasis.

"It has been a meticulously planned campaign from day one to establish the band as an international rock'n'roll act, very similar to the way Led Zeppelin were built up in the 1970s," he said.