Dozens of veterans of an elite Israeli military signals intelligence unit have said they will no longer serve in operations against Palestinians.
Forty-three past and present reservists signed a letter about Unit 8200, which carries out electronic surveillance.
They said the intelligence it gathered - much of it concerning innocent people - was used to "deepen military rule" in the Occupied Territories.
Israel's military said it held the unit to ethical standards "without rival".
Israel has occupied the West Bank and East Jerusalem, since 1967. It pulled its troops and settlers out of Gaza in 2005, though the UN still regards Gaza as under Israeli occupation.
Unit 8200 is the Israeli military's central intelligence gathering body and is often likened to the US National Security Agency (NSA).
The protest letter signed by the veterans of the unit was sent to Israeli Prime Minister Benjamin Netanyahu and armed forces chiefs.
The newspaper Yedioth Ahronoth quoted the letter as saying that unlike in other countries there was "no oversight on methods of intelligence or tracking, and the use of intelligence information against the Palestinians, regardless of whether they are connected to violence or not".
"We refuse to take part in actions against Palestinians and refuse to continue serving as a tool for deepening military rule in the Occupied Territories," the letter added.
"Intelligence allows ongoing control over millions of people, thorough and intrusive monitoring and invasion into most aspects of life. All of this does not allow for normal living, fuels more violence and puts off any end to the conflict."
The names of the signatories were not published, but they include officers, former instructors and senior NCOs.
Several told Israeli media that hey had been tasked with gathering private information - including sexual preferences and health problems - that could be "used to extort people into becoming informants".
They also claimed that some intelligence was collected in pursuit of the "agendas" of individual Israeli politicians.
The Israeli military spokesman's office said in a statement that Unit 8200 personnel were held to ethical standards "without rival in the intelligence community in Israel or the world", and had internal mechanisms for filing misconduct complaints, Reuters news agency reported.
That the letter writers went first to the media "raises serious doubt as to the seriousness of their claims", the statement added.
Former Israeli military intelligence chief Amos Yadlin dismissed the signatories as a "fringe percentage" of those working for Unit 8200.