The police have been urged to take urgent steps to uncover the true scale of gay hate crimes.
The Crown Prosecution Service has revealed just 12 people were prosecuted for homophobic attacks in Sussex in the 12 months to April.
But there were 114 crimes with a homophobic or transphobic element in the same period in Brighton and Hove alone, according to the city's Green Party.
Simon Williams, a gay member of Brighton and Hove City Council's Green group, said: "There are many factors that determine whether a case is prosecuted but I'm concerned at how few cases of homophobic crime are actually prosecuted relative to the far higher number of reported crimes."
He said hundreds of gay hate crimes were reported in Sussex every year.
Of the 12 prosecuted in Sussex, six defendants pleaded guilty. Of the six that went to trial, only two resulted in convictions while the other four were discontinued.
Coun Williams said: "In Sussex, this was a third of the total. The CPS admits that about a quarter of gay hate cases are discontinued because the victim withdraws the evidence.
"It's clear that some lesbian, gay, bisexual or transgender (LGBT) people who suffer hate crimes find the court process stressful or hostile so they decide to drop their case."
Coun Williams called for the police and courts to find out more about the LGBT community's experience of the justice system.
He said: "Sussex Police have developed effective reporting systems for victims of hate crime but the court experience may be taking its toll.
A police spokeswoman said: "We share the concerns. We have seen a steady increase in the reporting of such crimes in Brighton and Hove due to renewed confidence between the LGBT community and the police.
"However, the figures released by the CPS do not seem to reflect what the police are seeing, certainly in Brighton and Hove, and I will be researching this matter further to establish why this is."
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