The Met's community support officers (CSO) handed out less than one fine a day in London in one year, prompting concerns they are not properly trained.
CSOs can issue fines of up to £100
The figures for on-the-spot penalties, obtained by BBC London, show just 340 were issued by the 3,683 CSOs, between April 2006 and March 2007.
Glen Smyth, from the Met Police Federation, also said their "limited powers" hamper their work.
The Met said CSOs do more than issue fines and are carrying out a good job.
CSOs, who issue fines of up to £100 for offences like littering and graffiti, were introduced in 2002 by then home secretary David Blunkett.
In London, they can earn up to £25,000 a year and get specialist training.
The figures, obtained through a Freedom of Information request, shows less than one fine a day is being issued across London.
Mr Smyth said: "We're not surprised that the numbers are low because they're not supposed to be involved in law enforcement, they simply don't have the training for it.
"A lot of things are claimed about them tackling anti-social behaviour but whether the evidence is there remains to be seen.
"A uniformed presence is useful but those that indulge in persistent offending will simply take them on as they have limited powers and they are not police officers."
A spokesman for the Met said the teams the CSOs are part of give out a thousands of fines per year.
Commander Rod Jarman said: "I think they are extremely effective. They've made us much more connected to local communities, and they have helped us to engage much better with people in the long-term and build up enduring relationships."