The UK is due to deport up to 100 Tamils this week, despite warnings from human rights groups that they face torture from the Sri Lankan security services.
Human Rights Watch and Amnesty International have both voiced their concerns over the mass deportation of Tamils, which will be the UK's third since June.
Sky News has spoken to one man who was deported from the UK last year who claims he was tortured but managed to escape and get back to Britain.
He revealed lacerations on his back and burn marks on his chest - indicating that the UK's belief he would not be mistreated was wrong.
Going by the name of Hari, he said: "I was beaten up with plastic pipes, wires and batons. I was tied to a chair and burned with cigarettes.
"My head was covered in petrol... and I lost consciousness."
As a rebel Tamil fighter, Hari says he was subject to persecution and torture at the hands of the Sri Lankan government.
Campaigners say he is one of eight recent cases that prove torture is still happening, over two years since the country's 26-year civil war came to an end.
Brad Adams, Asia director at Human Rights Watch, told Sky News: "The British Government needs to be consistent.
"It claims that Sri Lanka needs to be held accountable at the Human Rights council in Geneva. But it's returning people to the possibility of torture.
"It has said that torture exists in the country, but because of its immigration policy, it doesn't want to keep asylum seekers in this country. So it's sending them back."
Protesters gathered outside the UN Human Rights Council in Geneva on Monday, demanding that the Council's 19th session discusses the situation.
Sri Lanka denies the claims, and has said men like Hari inflict the wounds on themselves in order to be accepted into countries like the UK.
But one of the Tamils scheduled to return to Sri Lanka on this latest flight told Sky that he was worried for his life.
His interpreter said: "The Sri Lankan forces have got his fingerprint, and they have his photo. They will maybe torture him, and kill him."
- SKY News