Illicit building has been taking place in well-established settlements, such as Ofra
The Israeli defence ministry has concealed information about the extent of illegal settlement-building in the West Bank, a leading newspaper reports.
A classified database of construction compiled by the ministry was leaked to the Israeli newspaper Haaretz.
It suggests most construction took place without the right permits, and more than 30 settlements were built in part on land owned by Palestinians.
Settlements are a contentious issue in the Israeli-Palestinian conflict.
The defence ministry has not commented on the report, which appears to contradict Israel's official position that it does not requisition private land for settlements.
The internationally-backed "road map" peace plan also calls on Israel to halt all settlement activity.
The database - compiled over about two years - was leaked to Haaretz by the Israeli human rights group Yesh Din.
It focuses not only on some 100 unauthorised settler outposts, but also on about 120 settlements officially authorised since Israel captured the territory in the 1967 Arab-Israeli war.
Israel says it does not tolerate the seizure of private land for settlements
An analysis of the data shows a big majority - about 75% - of construction in settlements was carried out without the right permit or in contravention of permits issued, Haaretz reported.
In more than 30 settlements, buildings including schools, synagogues and police stations, had been built on private Palestinian land.
The newspaper said Defence Minister Ehud Barak blocked publication of the data, arguing it could endanger state security or harm Israel's foreign relations.
Yesh Din told the BBC the report showed that the Israeli government ignored its own distinction between settlements considered legal under Israeli law, and illegal outposts built on privately owned land.
The group said it would use the information to help Palestinians sue Israel for damages.
The Haaretz article comes in the same week as the visit of the new US envoy to the Middle East, George Mitchell.
In 2001 he released a report which called on Israel to freeze settlement building.
Earlier this week Israeli Prime Minister Ehud Olmert was quoted in another newspaper as saying he had offered in talks with the Palestinians to remove 60,000 settlers from the West Bank.
Haaretz says the right-wing opposition leader Benjamin Netanyahu has vowed not to be tied to any pledges to withdraw settlers.
Jewish settlements in the West bank, including East Jerusalem, are considered illegal under international law, though Israel disputes this.