Assessment changes by UK Border Agency has led immigrants fleeing persecution to even show film of themselves having sex

Gay asylum seekers are increasingly going to extreme lengths to meet immigration officials' demands that they prove their sexual identity or else be returned to countries where they face persecution.

In a lecture to be delivered this week at the Law Society, S Chelvan, a barrister who specialises in asylum cases and works with the UK Border Agency (UKBA), will detail the extraordinary methods to which individuals are resorting – including filming themselves having sex – to justify requests for refuge.

The UK Lesbian and Gay Immigration Group (UKLGIG), which supports up to 1,000 applications a year, says altered official guidelines are a significant improvement but that they result in an excessive focus on the sexuality of individual claimants.

Changes introduced by the UKBA following a landmark supreme court judgment in 2010 have shifted the emphasis of official assessments to establishing whether or not claimants are genuinely lesbian or gay, according to immigration experts.

Prior to 2010, those seeking asylum because they were at risk if returned to states where homosexuality is illegal – such as Iran, Uganda or Cameroon – were refused permission mainly on the grounds that they could behave with discretion when returned.

Refusals are now more commonly made on the basis that claimants are not, or cannot prove, that they are gay, lesbian or transsexual, Chelvan said, explaining that the new focus is having bizarre and inhumane consequences.

"I know of at least two cases in the last six weeks where I have had asylum seekers filming themselves to demonstrate they are gay. Now it's all about proving whether you are gay or lesbian."

A Ugandan woman, who was eventually given temporary leave to remain in the UK but wished to remain anonymous, told the Guardian: "The UKBA officials wanted me to prove that I was lesbian but they wouldn't tell me how I could."

The woman, who spent months at Yarlswood detention centre awaiting deportation, said copies of a Ugandan newspaper that called for her to be killed should she return to the capital, Kampala, were initially disregarded by a UK immigration tribunal.

Erin Power, executive director of UKLGIG, said: "Many more people are now having their claims processed through a fast-track system while they are held in detention. We have argued with the UKBA that whatever you do sexually doesn't create the right identity.

"When [clients] tell us they have photos or videos … we say that's not how to establish their sexuality."

Around 75% of those who claim asylum on the grounds they are gay and will be at risk if removed from the UK fail in their claims, Power said. The failure rate has declined since new the guidelines were introduced. On occasions, she acknowledged, she had come across claims that she did not think were credible.

Jonathan Cooper, a human rights lawyer who is chief executive of the Human Dignity Trust, which campaigns to decriminalise homosexuality in more than 80 countries, said the asylum process was often "incredibly demoralising" and resulted in many people being sent back abroad where they were attacked.

Last month, he said, several men were lynched by a mob in Nigeria after allegedly being found having gay sex.

Figures on how many people seek asylum on the basis of their sexuality remain unknown. The UKBA has been asked to record and publish figures of how many claims are made but has not done so.

A UKBA spokesperson said: "We have changed our guidance to ensure that we do not remove individuals who have demonstrated a proven risk of persecution on grounds of sexual orientation.

"Our position remains clear – when someone needs our protection, they will be given it."

The president of the Law Society, Lucy Scott-Moncrieff, said: "We tend to think that, in terms of LGBT rights and protections, we've got it right. That in the UK, LGBT individuals have equal rights and are protected against discrimination.

"Yet there is a question whether these rights and protections apply to … asylum seekers who have fled to the UK because in their country of origin their situation is so dire, so desperate, that they fear for their own safety."