Siva, a Tamil from Sri Lanka, is facing deportation from the UK for the second time in two years. The last time he fought the journey every inch of the way.

"They loaded me on the plane first, right at the back, because I was making a lot of noise, screaming. I was very scared and begged them not to send me back but they said if I didn't go quietly, they would handcuff me and force me to go," he told the Guardian.

Given his account of what he had lived through in his home country, his panic is unsurprising. Since the brutal end to the Sri Lankan civil war five years ago, human rights groups have accused the government in Colombo of routinely abducting and torturing Tamils it suspects of sympathies with the defeated Liberation Tigers of Tamil Eelam (LTTE) insurgency.

Rape and sexual abuse of men and women is a factor in two-thirds of the cases studied by Freedom from Torture, the British advocacy group.

Siva was detained in a police station, tortured and forced to perform oral sex on his guards over a period of five weeks. He only escaped after his family paid a bribe. But, when he finally arrived in the UK, the Home Office did not believe his account. He was deported in 2012 after exhausting his appeals.

"I was confused and frightened. I couldn't sleep and was on sleeping pills. At first I thought I'd get a last-minute reprieve because twice before I'd been taken to the airport to be deported but not been sent.

"This time I realised it was going to happen when three people surrounded me and escorted me on to the plane and stayed there till it started to move. After takeoff I just sat there and didn't speak to anyone because I was too scared."

When he arrived at Colombo airport, he was interrogated by police for five hours, but they did not appear to be aware he had been in detention before and had claimed asylum. He was allowed to go, but soon the police came looking for him, forcing to him to flee and hide with friends in the tea plantations, never venturing outdoors. It was attending his sister's wedding in Colombo that was his undoing.

Police officers came for him on the second evening, arrest warrant in hand, claiming he had helped channel money to the LTTE when he'd worked in a shop in Colombo five years earlier and was now trying to reorganise a terrorist organisation.

"I don't know how to describe what went through my head at that moment; I was very scared. I cried and shouted but they handcuffed and blindfolded me and put a gag in my mouth to silence me. They started hitting me even inside the vehicle and put a gun to my head because they were angry that I'd hid from them. I knew I was going to be tortured again."

It started that first night at the police station in Colombo, with kicking, punching, slapping and beating with blunt instruments. Siva was hung upside down by his feet, his hands tied behind his back, and his head submerged in a barrel of water.

He was suffocated by having a plastic bag soaked in petrol tied over his head. He was, branded on several occasions with a hot metal rod, leaving 11 visible scars on his back, and burned with cigarettes leaving at least 17 visible scars.

An expert independent medical report subsequently obtained in the UK confirms Siva's scars are consistent with his account of torture. He also has the arrest warrant and court documents renewing his detention to prove he was indeed held in custody.

He was also repeatedly raped. "Even at night they didn't allow us to sleep; they sexually tortured us. I was raped by different men and sometimes other men watched. They were not wearing uniform and they were drunk. They called me 'Tamil slave' and 'son of a bitch'."

Ten months later, Siva's family again paid a bribe for his release, though the official police records say he escaped. Siva took a boat to India and then made his way back to the UK, arriving this year. When he went to the Home Office to apply for asylum again, he says he wasn't eligible because he had already been deported. Now he has to sign in at a police station monthly but every time he fears he could be detained again and deported.

In Sri Lanka, his parents also have to report to the police; as soon as Siva fled the island, his father and brother were detained. He doesn't know if they have been mistreated because they have never talked about it.

"If I am deported for a second time, I won't go; I'd rather die here. Because of the immigration people here I suffered more; they didn't take the right decision and because of them I was detained for months and suffered physical and mental torture."

Asked what he felt about the global summit on preventing sexual violence being held in London Docklands, a few miles from where he is staying, he said: "I feel like the British government has double standards hosting this summit; they are showing two different faces to the world."