The lifestyles of gay, lesbian, bisexual and transgender people in Iran are comprehensively and systematically denied by the Islamic regime, which exposes them to horrific punishment, bullying and risk of suicide, a study has found.

The first detailed report on Iran's LGBT community has found that its members live under social and state repression, with some being persecuted, forced into exile or even sentenced to death.

The study was conducted by Small Media, a non-profit group based in London. Researchers led by Bronwen Robertson, director of operations, gathered first-hand testimonies from hundreds of LGBT Iranians using face to face interviews or through a secret online forum.

"The bastions of the Islamic Republic of Iran fully realise that an established (albeit secretive) LGBT community exists beneath the folds of fundamentalism in [the country]," says the report. "[But] figuratively speaking, the Iranian government is doing its utmost to sweep the community under a densely woven Persian rug."

In a speech at Columbia University in New York in 2007, President Mahmoud Ahmadinejad said: "In Iran we don't have homosexuals like you do in your country … In Iran, we do not have this phenomenon. I don't know who has told you that we have!"

Yet homosexuality is punishable by death, according to fatwas issued by almost all Iranian clerics. Until recently, lavat (sodomy for men) was a capital offence for all individuals involved in consensual sexual intercourse. But under amendments to the penal code, the person who played an "active role" will be flogged 100 times if the sex was consensual and he was not married, while the one who played a "passive role" can still be put to death regardless of his marriage status.

Punishment for mosahegheh (lesbianism) is 100 lashes for all individuals involved but it can lead to the death penalty if the act is repeated four times.

Among the testimonies gathered by Robertson and her team was that of a 27-year-old gay man from Qazvin in the north-west of Iran. He said: "It's very hard to live as a homosexual in this country. Is it me or is it the culture, society, history or all of them? Loneliness is killing me."

Another said: "If I said I saw myself as being part of this society, I'd be telling the biggest lie of my life. I don't see myself as part of this society at all."

In September last year, three men from the south-western city of Ahvaz, the capital of Iran's Khuzestan province, were reported to have been executed after being found guilty of charges related to homosexuality. This week, there were unconfirmed reports of four men, identified as Saadat Arefi, Vahid Akbari, Javid Akbari and Houshmand Akbari, from Kohgiluyeh and Boyer-Ahmad province, being sentenced to death for sodomy.

Transsexuality was legalised in Iran in 1987. Yet the report warns that, despite state support for sex-change operations, "the social stigma attached to transsexualism is unwavering and transphobic abuse remains prevalent". It goes on: "Still very much ostracised, transsexual Iranians do not enjoy a privileged status in society."

LGBT Iranians have also fallen victim to the confusion within the Iranian society in regards to differences between being a homosexual and transsexual.

Parents have forced their homosexual children to have sex-change operations, local psychologists and psychiatrists who still deem homosexuality as a mental illness have prescribed cures.

This also exists within the regime with officials often confusing consensual intercourse with rape.

In cases when an execution involving sodomy charges is reported, it's difficult to find out whether the convicts were engaged in consensual sex or whether it's been a rape issue.

One of the contradictions surrounding LGBT life in Iran, is that homosexuals are granted military exemption on the basis that they are mentally ill which will prevent them from doing official work.

The report acknowledges that decriminalisation of homosexuality would not necessarily mean an end to LGBT discrimination. "LGBT issues are particularly taboo and are seldom discussed in Iran's public sphere," it said. "Even if Iran decriminalised homosexuality, it could take decades for it to become socially acceptable in the Islamic Republic of Iran."

As the result, many LGBT members in the country feel excluded from the society. "If I said I saw myself as being part of this society, I'd be telling the biggest lie of my life," said a 26-year-old Iranian gay man. "I don't see myself as part of this society at all. That's because of my homosexuality and the Iranian people's mentality about homosexuality ... I usually refer to Iran as 'your country' instead of 'my country' or 'our country'."

Human rights campaigner Peter Tatchell said: "[The Iranian LGBT community] show that, despite state repression and the frequent compromises they are forced to make to protect themselves, many Iranian LGBTs manage to get on with their lives and to forge a sense of community and solidarity."

Testimonials from Iran's LGBT community

I am a human being, but I was created with an imperfection. I'm someone that nobody wants to be friends with, someone that even her own family doesn't like … I've been unemployed for 2 years. Nobody will employ me because of the way that I am … I long to become a woman, get married, have a family and find a good job … I like to be surrounded by people, but people always reject me. It's as if I'm from another planet and they don't want to be seen with me. Male to female transsexual, 26 years old, from Lorestan

In my life I've trusted very few people, especially when it comes to my sexual identity, and those whom I've trusted have generally been homosexual too … In order to trust people, I need transparency and honesty more than I need time. Trusting people in the virtual world is much harder, because in the virtual world people can add an extra mask to those they already have and it's hard to figure out exactly who someone is and what their intentions are. Gay male, 22 years old, from Babol

I'd like to leave Iran; I'm getting pretty sick of people … Maybe I'd go to London or Irvine. I'd like to be a basketball coach, but to be a DJ would be my ideal job … in general I haven't had many problems but I often feel like I don't belong to society. Lesbian, 34 years old, Tehran