RAMALLAH, West Bank, March 15 (Noah Browning/Reuters) - The deteriorating health of a Palestinian prisoner on hunger strike for the past month is focusing international attention on Israel's decades-old use of detention without trial.

Shrouded by winter gloom, Palestinian protesters clutching pictures of Hana Shalabi gathered on Thursday outside Ofer prison, the largest in the occupied West Bank, and shouted slogans at Israeli soldiers guarding the facility.

The 30-year-old has refused to consume anything but water since being arrested in the West Bank village of Burqin last month and held on terms of administrative detention. Shalabi is now suffering spells of dizziness, muscular wasting and loss of consciousness, her lawyers and medical observers say.

Her protest is part of a spreading movement by Palestinian prisoners ignited in December by Khader Adnan who ended a near-fatal fast of 66 days after Israeli authorities agreed to cut his detention period.

Shalabi and Adnan are affiliated with Islamic Jihad, a militant group which earlier this week was engaged in days of combat with Israel in Gaza and the country's south during which more than a dozen of its fighters were killed by air strikes.

With Shalabi's condition serious, and 23 other Palestinians pledging not to eat while in Israeli custody, calls have mounted for Israel to repeal the controversial policy it has applied to detainees from the West Bank, which it has occupied since 1967.

Last month, Catherine Ashton, the European Union's foreign policy chief, expressed longstanding concern about the extensive use by Israel of administrative detention without formal charge.

EVIDENCE WITHHELD

In many instances, Israeli military authorities explain detentions in terms of their security concerns, and base cases on evidence from local informants or members of its own security services whose identities are not revealed.

Evidence isn't revealed and the way decisions against defendants are met is kept secret. Accusations and evidence are kept from the defendant and their lawyer, and the judge is made to act in the capacity of the defense, Naama Baumgarten-Sharon of the Israeli rights group B'Tselem said of the procedure.

Israel's High Court has upheld the procedure for decades, siding with the government's argument that detention without trial is a necessary security measure.

Israel, currently detaining some 300 Palestinians without trial, had held Shalabi for 25 months without trial but released her in October under a prisoner swap with the Islamist militant group Hamas.

This magic phrase, 'endangering public order' used by the Israelis to justify administrative detention is a dishonest instrument, Jawad Boulos, Shalabi's lawyer, told Reuters.

Some of those behind bars are not even accused of being violent, and their detention has more political motives.

Shalabi's legal team and the Israeli prosecution have failed to reach a compromise and a military judge is expected to relay his views on the case in the coming days.

In the meantime, the Palestinian government in Ramallah is asking for help from its foreign allies.

There are efforts ongoing. I spoke to the Egyptian side on the matter and [chief negotiator] Saeb Erekat has made contacts with the American side in the quartet, but what else can we do? This is a difficult issue, Isa Qaraqa, minister of prisoner affairs, told Reuters.

Islamic Jihad, an opponent of the Western-backed Palestinian Authority, said these efforts were falling short.

Official policy is not nearly enough, and they have not mobilized international institutions or rights organizations, said Jaafar Izzedine, Islamic Jihad's spokesman in the West Bank. They make statements, but nobody is moving. (Additional reporting by Ali Sawafta; Editing by Robert Woodward)