London's mayor is planning a Caribbean cultural event on the same weekend as the Notting Hill Carnival.
The Notting Hill Carnival has been going for more than 40 years
The Caribbean Showcase in Hyde Park on the August Bank Holiday weekend would cater for up to 5,000 people.
Lee Jasper, senior adviser to mayor Ken Livingstone said it will complement the Notting Hill Carnival and was not an attempt by the mayor to take control.
But a spokesman for the Notting Hill Carnival Trust (NHCT) told BBC News it was "very disappointed".
Mr Jasper said: "What was mooted is that carnival ought to start in Hyde Park. That has not been possible because of the logistics of route planning challenges.
'Disappointed and unhappy'
"So it was agreed a stand-alone event in Hyde Park, of a very small scale, could make a very successful contribution to the event."
But the spokesman for the NHCT said: "For the last year we have been in negotiations with the mayor's office to hold events in Hyde Park to complement the carnival.
"But we are very disappointed and unhappy that they have reneged on those discussions and decided to go alone. Their undertakings have been broken."
Asked if he thought it was an attempt by the mayor to take control of the carnival, he said there was "no point speculating", but said there were "difficulties" with Lee Jasper's office.
But he said if the Greater London Authority were to stop funding the carnival's stewards, it would increase the Metropolitan Police's costs.
A statement from the mayor's office said: "The Caribbean Showcase event in Hyde Park is a small scale event designed to celebrate the contribution of the Caribbean community to the life of the capital.
"Both the Metropolitan Police Service and the Royal Parks Police have been consulted and the events will not impact on policing levels at Notting Hill Carnival."