Hagit Ofran said the plans were adopted last week, and involve small settlements in the Ariel area in the northern West Bank, the Carmel settlement in the Hebron area and the Gush Etzion settlement bloc.
According to the NGO, the move marks the end of an informal construction freeze in the Palestinian territory that lasted 18 months.
Peace Now said on December 28 that Israel was working to revive and extend plans for new Jewish settler homes in the contentious area of the occupied West Bank known as E1.
In a report it said was based on government data obtained under a Freedom of Information Act request, the group said the housing ministry was seeking to build 55,548 units in the West Bank -- including two new settlements -- of which more than 8,300 homes would be in E1.
E1 and the adjacent Maaleh Adumim settlement form an Israeli buffer east of Jerusalem that the Palestinians say would divide the West Bank and badly hurt the possibility of a contiguous Palestinian state.
"The area of Maale Adumim and E1 is one of the most sensitive areas in terms of the chances for two state solution," Peace Now wrote.
"For these reasons, whenever an Israeli leader tries to promote the plans in E1, the international community strongly condemns them."
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The United States, the United Nations and the European Union oppose all Israeli settlement building but have voiced particular concern about plans for E1.
In 2013, faced with international pressure, Israeli Prime Minister Benjamin Netanyahu vetoed construction of some 1,200 homes there but Peace Now said the housing ministry had hired architects to prepare fresh blueprints.
"This planning, which contradicts any possible commitment to a two-state solution, continues," said last month's Peace Now report, although it also added that the plans could be years from fruition.
"They must be approved by the minister of defence and then go through the approval process of the planning authority," the English-language report said.
US-backed peace talks between the Palestinians and Israel collapsed in April 2014 amid bitter mutual recriminations.
A chief grievance of the Palestinians was settlement building on land they claim for a future state.
"The continued settlement growth raises honest questions about Israel's long-term intentions and will only make separating from the Palestinians much more difficult," US Secretary of State John Kerry said in a speech in Washington on December 6.
Israel seized the West Bank and east Jerusalem in the 1967 Six-Day War. It later annexed east Jerusalem in a move never recognised by the international community.
Today, some 380,000 Israelis live in 135 West Bank settlements, with another 200,000 in east Jerusalem.