The number of prisoners held under Israel's controversial administrative detention law has spiked because of a series of arrests since a new wave of violence began in October, the prisoners club said in a statement.
Under the administrative detention law, Israel can hold suspects without trial for periods of six months renewable indefinitely.
The system is again under the spotlight because of a hunger strike by journalist Mohammed al-Qiq, who has gone without food for 87 days in protest at being detained without trial.
The system has been criticised by Palestinians, human rights groups and the international community.
The United Nations Special Coordinator for the Middle East Peace Process, Nickolay Mladenov, raised the issue of administrative detention on Thursday in a speech to the UN Security Council.
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He said that anyone held under the system should "be either charged or released immediately".
He also said he was "deeply concerned about the deteriorating condition" of Qiq.
Israel says administrative detention, a policy it inherited from the British rule in Mandatory Palestine, is an essential tool for preventing attacks while allowing to keep sensitive information secret.
More than 7,000 Palestinians are currently in Israeli jails, including those under administrative detention, according to the prisoners club.
Among them are around 30 people who have been in jail since before the signature of the 1993 Oslo Accords.
The Palestinian Authority has made their release a condition of the resumption of frozen peace talks with Israel.