Jerusalem - The United Nations' Mideast envoy on Tuesday said a new Israeli law legalising dozens of unlawful West Bank settler outposts crossed a "very thick red line," while Israeli rights groups said they would fight to overturn the measure in the Supreme Court.The explosive law, approved by Israeli lawmakers late on Monday night, was the latest in a series of pro-settler steps taken by Israel's hard-line government since the election of Donald Trump as US president. It is expected to trigger a number of challenges in the Supreme Court, while members of the international community have already begun to condemn it.Peace dealThe law legalised dozens of outposts homes built unlawfully on private Palestinian land in the occupied West Bank. According to the law, Palestinian landowners would be compensated either with money or alternative land, even if they did not agree to give up their property.Critics say the legislation enshrines into law the theft of Palestinian land. It also marked the first time that the Israeli parliament has imposed Israeli law on Palestinian inhabitants of the West Bank. The area, captured by Israel in 1967, is not sovereign Israeli territory and Palestinians there are not Israeli citizens and do not have the right to vote.Nickolay Mladenov, the UN's co-ordinator for the Middle East peace process, said the legislation "opens the floodgates to the potential annexation of the West Bank." If Israel moves to solidify its control over the area, it would imperil the internationally backed idea of establishing a Palestinian state alongside Israel as part of a negotiated peace deal, he said."It will have a drastic legal consequence for Israel and for the nature of its democracy," Mladenov said. "It crosses a very, very thick red line."Britain's minister for the Middle East, Tobias Ellwood, condemned the law, saying it "damages Israel's standing with its international partners." He spoke a day after Israel's prime minister, Benjamin Netanyahu, met British Prime Minister Theresa May in London.The law also cast a cloud over a visit to Israel by Turkey's tourism minister. Israel and Turkey recently repaired ties after a six-year rift and the tourism minister, Nabi Avci, was visiting as part of that reconciliation.Softer approachAsked about the law, Avci said he hoped Israel's Supreme Court would strike it down. "I think, I hope, that on this issue, the high court will make the right decision...a decision in accordance with international law...a decision in accordance with United Nations decisions," he said.Prime Minister Benjamin Netanyahu's nationalist coalition is dominated by West Bank settlers and their allies. After repeated clashes with President Barack Obama, they have grown emboldened by the election of Trump, who has signalled that he will take a much softer approach toward the settlements than his predecessors or the rest of the international community.