Charities that pay for golden bonds are guaranteed places for runners in the UK's most lucrative fundraising event, provided the runners agree to raise a specified sum. There are currently 600 charities on the waiting list for a golden bond place, and only six charities failed to renew their bonds last year.
The only other way to get runners into the race is to take part in the main ballot system for all runners. The society complains that it takes part in the ballot for Marathon places every year, but the odds on getting a place are only around one in 10.
London Marathon race director David Bedford, responding to a letter from the society, said the golden bond scheme would continue to be run on a first come, first served, basis. "We have considered a number of proposals for restructuring, but in each case this obviously has a knock-on effect for existing charities involved," he wrote.
The scheme began in 1993, and the limit on entries was reached in 1999.
Once a charity has a golden bond - which gives it five places for five years - it can renew it as often as it likes.
A fundraiser at the society, Philip Bush, said: "In June 2003, we were number 268 out of more than 500 charities on the list. In April 2004, we were still number 268, but now out of more than 600."
A London Marathon spokeswoman said that because of over-subscription, no new charities had been allocated bond places in 2004.
The society is proposing a one-year bond, handed out every five years or so, giving the charity five guaranteed places for one year.
"If other charities feel the same way we will have a stronger case for urging change with the London Marathon," added Bush.