By Richard Miron
BBC Radio 4's Crossing Continents
The knowledge that thousands of Palestinians may be working covertly for Israel's internal security services is leading to paranoia and murder in the West Bank.
Palestinian militants: Israel says its informers prevent attacks
Adel Ahmed rarely has visitors to his home in the village of Kfar Deek in the West Bank.
He and his family are shunned by their neighbours.
"We don't have a relationship with anybody in this village," he says bitterly.
Adel and his family are considered to have committed the greatest crime in Palestinian society - collaboration with Israel.
He vigorously denies the charge. But he has paid heavily for his alleged crime, losing his livelihood, his social position and one of his sons.
Over cups of bitter coffee in the shabby and neglected lounge of his house Adel tells his story.
His trouble began, he claims, after his sister was molested by some Palestinian Authority officials.
He then complained to the government only to have the officials turn on him and accuse him of collaborating with the Israelis.
"It destroyed our family, alienated us and destroyed us," he says quietly.
Adel was arrested by the Palestinian Authority and according to him was tortured. Half his teeth were knocked out and his arm broken during his interrogation.
Then he says his eldest son was taken and also tortured. Next they came for his youngest boy - only 12 years old - who was subjected to similar treatment: his arms were burnt with melted plastic and cigarettes.
The boy sitting quietly on the sofa listening to his father gets up and displays small round scars near his wrists as evidence.
Finally, he says, masked men abducted his middle son Shafi as he was on his way to the pharmacist to buy medicine for his mother.
The next time Adel saw him, he lay dead in the road near the village having been shot 14 times.
Fight for justice
Adel Ahmed sits surrounded by pieces of paper - his son's autopsy report and copies of the numerous letters he has written to the Palestinian Authority in an effort to clear his family's name.
Nothing is more important to him than proving the allegations against him and his family are untrue.
"The truth is the only way out," he murmurs.
Suddenly his voice rises and he says insistently:
"Shafi was not a collaborator. If anybody now can bring proof of his collaboration I will go to the grave, I will dig him out and throw him to the dogs."
According to a Palestinian human rights group, Adel Ahmed's experience is increasingly common.
Amid the growing chaos in the West Bank, it estimates that approximately one person a day is killed having been accused of collaborating.
No-one has been arrested following any of these killings and many Palestinians say that the charges are normally false.
However, with the breakdown in law and order, the accusation has become the excuse for revenge and bloodletting.
Shame and shadow
Finding out about the collaborators is no easy task.
It is shrouded in shame in the Palestinian Territories and in secrecy in Israel.
The Shin Bet, Israel's clandestine security agency, has a network of collaborators, or "assistors" as it prefers to call them.
The organisation operates in the shadows and does not advertise its existence.
Getting an interview is no easy matter but, following numerous contacts, the Shin Bet did agree to meet the BBC.
The meeting took place not at the Shin Bet headquarters but rather at a neutral location - a conference centre in Tel Aviv.
Upon arrival I was greeted by a number of people - and informed that I could not record the meeting or ask specific details about how the Shin Bet ran its network of collaborators.
I was then introduced to some agents.
One of them known as "Mike" has overseen collaborators in the West Bank. He told me about the care he said Israel took to look after its informants.
Mike was affable and articulate and could easily have been mistaken for an lawyer for his ordinariness, rather than a spy.
But he was insistent on the value of the information the collaborators have provided.
"They've saved many lives by preventing suicide attacks," he said.
Mike represents the polished public face of the Shin Bet.
For Palestinians the organisation is hated and feared for its ruthlessness and efficiency.
One former Shin Bet agent who spoke off the record described the collaborators who used to work for him as lemons:
"You squeeze the lemon and [when] it's got no juice left, you throw it away."
Life for the collaborators and for those innocents even suspected of working for Israel is one of deception and increasingly one that brings death.
Crossing Continents was broadcast on Thursday, 14 December 2006, at 1102 GMT and repeated on Monday, 18 December 2006, at 2030 GMT.