Presenting his second report since the resolution was adopted in December, Nickolay Mladenov told the Security Council that "no such steps have been taken" to end settlements.
"Since March 24, there has been substantial increase in settlement-related announcements as compared with the previous reporting period," he said.
Israel is moving forward with plans for nearly 4,000 housing units and has issued 2,000 tenders for settlement construction in the occupied West Bank and east Jerusalem, he added.
US Ambassador Nikki Haley has branded the resolution a "terrible mistake" after the previous US administration refrained from using its veto to block the measure.
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The resolution was adopted with 14 votes in favor and one abstention from the United States at the 15-member council.
The envoy's report to the council came on the same day as Israeli Prime Minister Benjamin Netanyahu announced the start of work on the Amichai settlement in the northern West Bank.
President Donald Trump's special representative Jason Greenblatt arrived in Israel for meetings on relaunching Israeli-Palestinian peace talks that collapsed in 2014.