Switch-hitter, licker of both sides of the stamp, or even just downright “greedy”. When you’re bisexual you’re used to being defined by your presumed sexual treachery. Even the term bisexual, unlike gay or lesbian, has the sex act at its core: you can’t escape from the sense that our very presence on the streets is solely informed by our exploits between the sheets. Of course, the reality is that bis want emotionally honest love and relationships, friendship, satisfying work, and good physical and mental health like everyone else. But, as I have just found in Being Bisexual, a documentary I’ve made for the BBC World Service which airs today at 1.30pm, we are at risk of being seriously sidelined in the worldwide campaign for L, G and T rights.

Invisibility is a core problem. Bisexuals are frequently told by gay and straight people alike that they are “lucky” to be able to forge an identity as heterosexual if they so choose and hide their same-sex attraction when it suits them. But in countries such as Iran – as campaigner Sudaran of the country’s only Farsi-language bi website Dojensgara, whom I interviewed for the documentary helped me discover, it’s a homosexual act, not homosexual identity, that is punished with imprisonment and even death, meaning that bis face exactly the same threat – only without the same recognition of the problem.

Even in more relaxed countries, “passing” privilege comes with its own negatives. The reality is you can feel in denial of a core part of your identity, and isolated from others who would understand your position, whether you are out or not. Bi people are still more likely to be hidden from one another and society at large than gay or straight people. Research from the US Pew Research Institute in 2013 found that more than 80% of bisexuals end up in straight relationships, which I think tells you something, not about the fleeting or transient nature of bi identity, but the slow-drip pressure to conform when there simply aren’t enough bi relationships to model your own on.

And while bisexuals may not be subjected to the same kind of overt abuse that gay or trans people face, prejudice also regularly comes from the L, G and T community as much as from straight people. An ex-girlfriend who prided herself on being a “gold-star lesbian” even used to laugh about having to “scrub me clean” when she first met me. You’d think someone used to being marginalised themselves would do better than to show such prejudice.

An ex-girlfriend who prided herself on being a ‘gold-star lesbian' used to laugh about having to ‘scrub me clean'

Which brings me to another core problem – bi-erasure. Later, the same ex-girlfriend was incredibly hurt herself when she discovered that I had been asked to leave her out of Bound to You, the sexual memoir I went on to write, on the basis that adding bisexuality into a story that already included escapades in BDSM sex work would confuse the reader. It felt gut-punchingly wrong. And yet, as a fledgling author desperate to please, I rationalised it on the basis that I hadn’t included every single male lover either.

Now I realise I was complicit in my own bi-erasure. Sharing stories with my interviewees as I made this documentary, I learned just how common it is to downplay one’s bisexuality, even to oneself. Interviewing my own very liberal mother for the programme, I confronted her about how she’d once uncharacteristically become upset that I might not have the husband and 2.4 children she’d presumed for me, even uttering the cliche, “It’s just a phase”. Apologising, she ended the interview by coming out as bi herself.

What the individual invisibility and erasure create is a communal blank. When I researched the history of LGBT dating for my latest book on the history of dating, it was the bi stories that proved the most elusive. After the first world war, I discovered, there had been a cohort of young professional women who solved the issue of what to do about the drastically reduced male population by coupling up with one another. I’d never heard or read about this history until I dug it up from the annals myself. How many other examples are there?

The truth is, we can’t know because the media often becomes inadvertently complicit in the erasure. Despite a month of LGBT programming by all the UK broadcasters to celebrate Pride and 50 years since the decriminalisation of homosexual sex, ours was the only programme on a major network solely dedicated to bisexuality. In mainstream TV and film, bi-erasure is so prevalent that even I can count on one hand the number of famous bisexuals or bisexual characters I’m aware of in current programming. For this reason it was heartening to interview Tim Manley about his show The Feels, which relates the travails of being a bisexual man. And even more heartening that his straight friend Nadje was by his side in production, helping him to tell his truth and to add to the palimpsest that is bi history.

Which brings me to the final issue. Bi men and women are lumped together in identity and campaigning, but in many ways their struggles are as disparate as gay men and lesbians. For women, the major presumption you encounter from people you are both dating and not dating, is that you’ll be the first up for a FFM threesome. For men, it’s that they’re secretly really gay but not yet ready to properly come out as such. The fact that there are fewer self-declared bi men than women must surely be related to the sniggering reverence with which we treat female bisexuality. It’s telling that even in the eight years I’ve spent working as a sexual politics journalist, I can count the number of openly bi men I’ve met on one hand.

What’s more, there’s compelling evidence to suggest bi people suffer mental health problems precisely because of biphobia and invisibility, often reporting a higher rate of anxiety, depression, self-harming and eating disorders than gay and straight people alike as a result.Combine this with the fact there are 76 countries in the world where homosexuality and by proxy, bisexuality, remains illegal, plus the differing sexual health needs facing bisexuals and you begin to get the picture of the pressing need to speak more, not less about the “B”.

Now that fluidity is the watchword, there’s a sense that bisexuality is essentially an anachronism, that fighting for a distinct identity and better representation is missing the sexual identity lifeboat. But for thousands of bisexuals the world over, the label is precisely the lifeline they need.