The parents of a British student extradited to Greece to face manslaughter charges have spoken of his “nightmare” ordeal in jail.

Andrew Symeou, 20, was imprisoned in a tiny cell and forced to sleep on a concrete block with five other prisoners in police detention on the Greek island of Zante, his father Frank said last week.

Symeou, from Enfield, north London, is accused of killing a fellow British teenager with a punch in a Zante nightclub in 2007. He was extradited 10 days ago under the fast-track European arrest warrant.

Under the scheme, introduced in 2003, UK citizens can be extradited to other European Union states without a British court having to see the basic evidence against them. Symeou’s parents said this weekend the evidence against Andrew had been fabricated by local police officers who beat admissions out of two witnesses.

They said their son was a victim of mistaken identity and that there were eight witnesses who would testify that he was hundreds of yards from the scene of the crime.

Last week Gary McKinnon, a 43-year-old who suffers from Asperger’s syndrome, lost a High Court bid to avoid extradition to America. He is wanted on charges of hacking into US military networks.

His supporters, who include 40 MPs, describe McKinnon as “a UFO eccentric” who had been searching for evidence of extra-terrestrial life.

Symeou now has the backing of Liberty, the human rights group, and of several politicians who are campaigning for his release, claiming the case is a gross miscarriage of justice.

His barrister, Edward Fitzgerald QC, has described the case against him as “tainted” by fabricated police evidence.

In a series of e-mails and an online diary written for family and friends, Frank Symeou, the joint managing director of an architectural and interior design company, described the emotions of father and son during a fleeting reunion through the bars of his cell.

“When I went to see Andrew, my heart broke again. I’m not sure how many pieces it’s in now. What I do know is that it will take a lot for it to heal.”

Describing their first visit, he said: “Helen [Andrew’s mother] saw him first and later I was allowed, but only for five minutes. He was in distress and looked terrified, but to me he was putting on a brave face.

“He did shed a tear with his mum saying that Patras [where he spent his first night in a Greek cell] was a terrible experience and that he was treated with contempt. He was taunted for being British. He was not allowed to change his clothing until today, but still hasn’t showered.

“The cell is about [11ft by 15ft] with a solid concrete slab. The blankets are flea-ridden. We were only allowed to talk to him through the bars.”

Despite 37C temperatures, there was no fresh air, just a tiny window welded shut.

Frank Symeou said his son was later moved to a cell housing five other prisoners, illegal immigrants from Albania.

“Andrew did not look good and was not coping well ... He seemed to be struggling to keep it together,” he wrote in his diary.

At Patras, where Symeou was detained after being flown from Britain to Greece, police refused to give him the antidepressant medicine he has been prescribed by doctors.

Symeou is accused of punching Jonathan Hiles, 18, from Cardiff, during an incident at the Rescue nightclub while both were on holiday on Zante in July 2007.

The family’s lawyers said eight witnesses would testify that Symeou was in a different nightclub, hundreds of yards away at the time.

Hiles’s friends told police the assailant was clean-shaven. Yet evidence shows Symeou had a full beard the night before the attack and at his sister’s graduation four days later.

CCTV footage, said to have shown the attackers fleeing the club, has disappeared.

Two of Symeou’s friends said police beat them until they incriminated him.

Shami Chakrabarti, director of Liberty, said: “The shocking story of Andrew Symeou highlights the injustice of instant extradition.

“No one should be plucked from their home and dragged across the world without even basic evidence being shown in a local court.”

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