Supergrass headlined the Sunday night

But organisers said the changes were made because the site was waterlogged and was not safe for crowds.

"A number of acts did not appear. There were notices outside the site saying people could get refunds if they did not go in," a spokesman told BBC News Online.

But organisers are refusing to offer money back to those who went through the gates.

Bands including One Minute Silence and Hell Is For Heroes were also removed from the bill.

The remaining groups played in four tents, not the original six - despite the fact that all six stages were open on the other two days of the festival.

Scores of fans have posted angry messages on the internet and signed an online petition, started by one festival-goer, Owen Lloyd-Jones.

The dance and roots days both sold out

"The promoters are refusing refunds, claiming that the bands were pulled off for safety reasons, despite the fact that all the bands cited contractual difficulties as the reason and the fact that there has been very little rain in the Bristol area recently," he said.

"Anybody who cares about music must combat this growing trend towards mistreatment of people who are paying out lots of money for services they are not receiving."

But organisers say Reef and Therapy? will play at the second Essential Festival of the summer - in London in August - and those with unused tickets from Bristol may get free passes for that event.

Legend

Britpop band Supergrass headlined on Sunday, with other bands including The Beta Band, Hundred Reasons and The Levellers also playing.

Saturday saw dance acts play, headlined by rapper Busta Rhymes, while the bank holiday Monday was a roots day, headlined by soul legend James Brown.

Some 15,000 tickets were available for each day, costing �35 each.

The dance and roots days were sold out, the organisers said, but the rock day was not.

The Essential Festival has undergone several years of turmoil, after being forced to relocate from its original home of Brighton to Hackney Marshes in London in 2001 because of foot-and-mouth.

Did you go to the Essential Festival in Bristol? What were your experiences? BBC News Online would like to hear from you.