Overseas strippers, prostitutes and escorts are being invited to attend classes, which also help improve their patter with punters and help boost their safety dealing with landlords.
Hundreds have taken up the offer to learn from sex worker-led co-operative X:talk, who launched the idea several years ago in London.
Students learn from sex leaflets containing X-rated slang and sex jargon, while also taking part in role plays to work on their language.
Former escort Ava Caradonna, 35, is one of five teachers behind the project - although that isn’t her real name.
She told Time Out magazine: “The project grew out of the experiences of Alice, a prostitute who worked with many women from Thailand.
“They had difficulty negotiating with clients about sex acts they didn't want to perform.
Another of the coaches Katrin, 28, added: “Some of the escort workers have quite good English but they might need to be able to talk to the client for a whole evening, or even a weekend, and to talk about quite sophisticated topics.
“Other students’ needs are basic. Learning English makes them more confident because they can negotiate safer sex acts, and fair rents for their rooms with their landlord.”
Speaking after a class, transgender Romanian sex worker Katya said: “Sometimes I find it difficult when people use slang, which their's a lot of in my work.
“So the classes are really helpful and hep me with everyday things like making appointments.”
And lapdancer Isabel, 25, added: “We can talk about issues freely - the instructors are very patient and respectful.”