More than half the wheelchair users with tickets for London's Live 8 concert will be unable to attend, due to insufficient allocated space.
The disabled platform offers the best possible view of the stage
Some 300 disabled ticket-holders have applied for 140 available spaces.
Promoters say regulations laid down by Westminster Council restrict their wheelchair-users' platform's capacity.
But the council says the promoters decided the platform's size and it would be happy for it to be widened to accommodate more wheelchair users.
Jane Townsend, of London, told BBC News she was one of more than 300 disabled ticket-holders who had applied for the spaces at the Hyde Park concert on 2 July.
"It is not encouraging for poverty when even disabled people cannot be helped," she added.
Live 8 publicist Bernard Doherty told BBC News a platform had been constructed to offer the best possible view of the stage but its capacity was restricted to 140 wheelchair users and 140 of their carers by regulations laid down by the licensing authority for the event, Westminster Council.
"We are very sorry - but the platform is now full," he added.
But a Westminster Council spokesman told BBC News: "We take umbrage at the suggestion we told them how big the platform could be - that is up to the promoters and should be based on the number of people who want disabled access.
"We are surprised they are saying we are responsible for the decision.
"We would be more than willing for them to widen the platform, provided it satisfied health and safety requirements."
Mr Doherty told BBC News there were already twice as many places allocated to wheelchair users and their carers as there had been at the last annual Prince's Trust Party in the Park concert in Hyde Park, which was attended by 100,000 people.
The existing platform had access to disabled toilets and refreshment stands, and a shuttle bus would carry people to and from free disabled parking spaces, he added.
About 150,000 people have won tickets to the Live 8 concert, following a text message competition.