In an olive grove on the edge of Nablus, Fuad Amr and his sons keep one eye on the branches they are stripping and the other warily on the Jewish settlement that overlooks their land from a hilltop.

The settlers could descend at any time to intimidate them or even beat them and steal the fruit of their labour, as happens every year across the West Bank in the olive season.

The Palestinian farmers, however, have found unlikely allies - Jewish activists, some of them Orthodox rabbis, who risk violence to protect them.

“I am afraid,” Mr Amr said, as he flung black olives on to a plastic sheet, from which his wife gathered them into a sack. “I’m picking the olives and all the time I’m looking out for settlers. They come in buses, sometimes 20 or 30 of them.”

Last year one of his neighbours was hit on the head by a rock thrown by settlers, who cite the biblical-era Jewish settlements in the area as a claim to the land.

Every year, however, Israeli and foreign peace activists come to protect the Palestinians during the harvest and help them to pick their crops. Some of them have also been beaten by settlers, but they say that their presence prevents the Palestinians from being driven off their fields.

One of the Jewish groups is Rabbis for Human Rights, which aims to promote religion as a point of harmony and justice between Jews and Arabs.

“For us it’s a never-ending task to do the right thing,” David Nir, an Israeli physicist, said. He added that the bitter, low-level struggle fought in the olive groves and fields on the West Bank was wearing down many activists, with fewer showing up these days. “In the last two years I’ve seen people express despair,” he said.

That despair was echoed in a report this week by Peace Now, the chief Israeli antioccupation group, which said that despite Israeli pledges to curb the growth of settlements before a forthcoming US-sponsored conference, Jewish communities in the occupied territories continued to grow. Of the 122 settlements in the West Bank, Peace Now says that 88 are carrying out building work, mostly in the larger settlement blocks that Israel intends to hold on to in any deal with the Palestinians.

The report says that settlers are building at least ten more permanent structures in some of the 105 unauthorised outposts built in the West Bank since the 1990s, creating what they call “facts on the ground” that will prevent the land from being returned to the Palestinians.

The Middle East “road map”, a peace plan that Washington hopes to revive in the coming months, requires Israel to dismantle all unauthorised outposts built since March 2001. Fifty-one settlements fall into that category, according to Peace Now.

“All that Israel is doing on the ground is an obstacle to all that we are trying to achieve,” said Rafiq Husseini, an adviser to Mahmoud Abbas, the Palestinian President.

Mr Nir, the peace activist, said that Israel was complicit in the violence that haunted the Palestinian olive-pickers every year: “It's the Government. They want to humiliate the Palestinians . . . The hidden agenda of Israel is to take as much as possible of the land.”

As the Sun set, Mr Amr and his sons headed home, glad that the day had passed without incident and grateful for the meagre protection afforded by the Israeli activists.

“I feel good about it,” he said. “They help us and protect us from attack by the settlers.”