Israel is holding 1,201 Palestinians under administrative detention without charge or trial – the highest number since human rights groups began collecting monthly data in 2001, according to Israeli Prison Service data obtained by rights group HaMoked.
The figures also showed that administrative detainees account for a quarter of all Palestinian prisoners held by Israel. Administrative detention orders typically last for terms of three to six months but can be renewed indefinitely.
Intelligence used to justify the detentions is not disclosed to the detainees or their lawyers.
"Administrative detention is supposed to be an exceptional measure, but Israel uses it extensively for Palestinians," Jessica Montell, executive director of HaMoked, was quoted by Haaretz as saying.
"In the past year, it has crossed every boundary – a quarter of Palestinian detainees are in administrative detention. This is an unprecedented and worrying situation.
"We are talking about detention without trial based solely on classified material, without effective judicial review and which can be extended indefinitely. This is arbitrary and clearly unacceptable detention."
There are currently 5,014 Palestinians in Israeli jails, according to Israeli Prison Service figures. Less than half - 2,353 - of those prisoners have been tried and sentenced, while 1,460 of the inmates are undergoing legal proceedings. The rest are held under administrative detention.
Those held under the controversial practice include former prisoners, women, children, elderly and sick Palestinians, according to the Palestinian Prisoners Club (PPC).
On Thursday, administrative detainees at the Ofer Prison in the West Bank began a protest against their continued detention, the PPC announced. The protest is planned to be the beginning of a broader campaign of disobedience in Israeli jails.
The PPC highlighted that this action is taking place as at least 60 prisoners continue their boycott of Israeli courts.
The Committee for Administrative Detainees, a cross-factional prisoner group, said the prisoners will decide when to begin a mass hunger strike to escalate their protest.
Israel has carried out a series of brutal raids and attacks on the West Bank and the besieged Gaza Strip this year, which have been accompanied by an increase in Palestinians detained under administrative detention orders.
According to B’Tselem, the number of Palestinian administrative detainees was higher in 1989 during the First Intifada, at 1,989.