The event, which last year drew 250,000 people, is due to take place on 4 July. But it is understood that the controversial decision to make it a ticket-only event, which has split the gay community, has caused the problem, with few people wanting to pay pounds 5 for admission.
The lack of ticket sales is a major disappointment for the organisers, who brought in Harvey Goldsmith, one of the most experienced players in ticketing and events, to help them organise this year's Pride.
Until now both the march through central London and the after-march party on Clapham Common in South London have been free.
The letters pages of the Pink Paper, a gay weekly, have resounded in recent weeks with the outcries of angry readers. They have been calling the Pride hotline to be greeted with the recorded message: "No ticket, no entry".
The organisers, Pride Events Ltd, said on Friday that one third of the 100,000 tickets have been sold and there are still two weeks to go. A spokeswoman, Lotty Fitzgerald, said the decision to charge for tickets was essential to prevent cancellation of the event.
"It was a choice between charging and the whole day not happening and we think that pounds 5 is a pretty fair price for all the entertainment. It's going to be more elaborate and camp than ever this year," she said.
"Last year's event, which was run by a different company, made a loss because people were only asked to give a pounds 3 donation but hardly anybody did, so the organisers ended up with lots of debts."
Neither she nor the local authority, Lambeth Council, would elaborate on the festival's current position, saying only that an official statement would be made tomorrow afternoon.
The decision by Lambeth Council drastically to reduce the attendance allowance on the Common from 250,000 to 100,000 - made on environmental, health and safety grounds after discussions with London Transport and others - has not gone down too well either.
The council has come under pressure from local residents, who have complained about the impact of the event on their neighbourhood.
Others, however, have protested at a charge being made to go on to common land.
Harvey Goldsmith, who is one of the directors of Pride Events, was not available for interview.
Pride Events said he was invited to join them to help steer the festival "because - although being straight - his impressive track record in dealing with big open-air events and his support of the lesbian and gay community, makes him a valuable member to have on board".
Mr Goldsmith gained almost legendary status for staging concerts by Bob Dylan, The Rolling Stones and David Bowie. Most notoriously he helped Bob Geldof make the worthy television marathon Live Aid one of the biggest fund-raisers of all time, collecting pounds 140m.
More recently he applied his Midas touch to put the Three Tenors on stage at Wembley and Pavarotti in Hyde Park, and has been involved in both the Freddie Mercury Aids Benefit and the Elton John Aids Foundation.
If the event does not go ahead London will lose one of its most colourful events - an annual opportunity for gays and lesbians to meet en masse and celebrate in a carnival atmosphere.
At present the march is due to step out at noon on 4 July from Carriage Road along Hyde Park's southern edge and wind down Piccadilly, Trafalgar Square, Parliament Square, Millbank and dispersing at Marsham Street. Special bus services will operate between central London and Clapham Common.
BBC's Radio 1 will be broadcasting live from the event for the first time this year, with two of the station's DJs, Judge Jules and Danny Rampling.Reuse content