There are plenty of thorns in the side of the peace process, but none as sharp and intractable as Israel's settlement programme. For decades, successive Israeli governments have persisted in their obstinate policies in the West Bank to the detriment of civilians on both sides, despite knowing full well that no lasting peace deal can ever be reached without an end to the settlement enterprise.

Although the settlements are deemed illegal under international law, Israeli officials continue to cling to their belief that Israel has every right to settle its citizens in expropriated land over the Green Line. One line of argument employed by settlement supporters is that no settlement is built on private Palestinian land – though such a claim appears to be based largely on settler fiction rather than hard facts.

According to a new report by the Israeli human rights group, B'Tselem, over a fifth of built-up settlement areas are constructed on privately owned Palestinian land, giving the lie to the assertions of settler leaders that their actions are entirely above board. B'Tselem's figures are based on official government records which reveal a state-wide complicity in the wholesale violations of local and international law – and the deception has been going on for years.

When sanctioning early settlement construction in the West Bank, the report says:

"the principal means Israel used ... was declaration of 'state land', a mechanism that resulted in the seizure of more than 900,000 dunams of land (16% of the West Bank), with most of the declarations being made in 1979-1992. The interpretation that the State Attorney's Office gave to the concept 'state land' in the Ottoman Land Law contradicted explicit statutory provisions and judgments of the Mandatory Supreme Court. Without this distorted interpretation, Israel would not have been able to allocate such extensive areas of land for the settlements."

When I interviewed prominent figures in the settler movement for my book on Israeli settlements, I was met time and again with the declaration that settlements are "more legitimate" than major Israeli coastal cities, in a paradoxical interpretation of Israeli law. "In Haifa and Tel Aviv, they took over Arab property. But the settler movement wasn't allowed to touch private property", said Daniella Weiss, mayor of the Kedumim settlement and a long-time settler figurehead.

"One of the backbones of the settler movement, according to the guidance of Rabbi Kook, was that we could only build on rocks – not on people's private land … Now as there was a lot of rocky land, the settlers, including me, settled on the rocks," she explained as she recalled the founding of Kedumim in the mid-1970s.

From rocks to riches, the settlement enterprise has covered vast amounts of ground in the succeeding years with people like Daniella at the helm. However, somewhere along the line the guidance of Rabbi Kook has gone unheeded, because according to official Israeli Civil Administration data obtained by B'Tselem, 21% of built-up land in the settlements is private, mostly Palestinian land, while in Kedumim itself that figure is over twice as high, according to Peace Now figures. If Daniella Weiss was aware of this fact, she chose not to mention it.

It is a similar story across the West Bank, with scores of other settlements built illegally with government approval, and the crimes compounded by continued state assistance to those residing within the illicit communities. One such settlement is Ma'on, in the South Hebron Hills, where buildings have been constructed without permission, with civil administration data revealing that 15% of the settlement is built on private, mostly Palestinian, land. Similarly, the settlement's outpost, Havat Ma'on, which is illegal even according to Israeli law, is not only built without permission, but also extends on to private Palestinian land, with all the resulting hardships on the local Palestinians that such encroachment brings.

According to Israel's Road Map commitments, the outpost is supposed to have been demolished, and yet it continues to be supplied with water, electricity and defence by the Israeli authorities. Moreover, even if the government was inclined to evacuate the outpost as it is committed to do, evacuations in the past have simply resulted in the transfer of the population to other West Bank settlements in the Occupied Territories.

There is little point in expecting the settlers themselves to up and leave their cushy, state-subsidised homes as long as there is no official pressure on them to do so. A dogged and dogmatic commitment to illegal settling of the West Bank is the nature of the settler beast: to expect a volte face to come from within the settler community is wildly unrealistic. Instead, the onus is on the Israeli government to pull the rug from beneath the settlers' feet, in order to demonstrate serious commitment to the peace process and to prove to the Palestinians that Israel is prepared to make painful concessions in the name of ending the conflict.

While it is all well and good for Israelis to demand an end to Palestinian violence and sabre-rattling, there has to be goodwill shown from the Israeli side too – and no amount of words can speak as loudly as the action of a large-scale pull-out from West Bank settlements. Without such a step forward, the region is doomed to forever stagnate in a cycle of stalled road maps and failed efforts, and there will be no peace for both the wicked and good alike, on either side of the divide.